1:50 p.m.

German airline Lufthansa says its Friday flight from Frankfurt to Tehran is cancelled "as a precautionary measure" because of the security situation for airspace around the Iranian airport.

The same flight turned back Thursday for the same reason as investigators rush to determine what brought down a Ukrainian airliner this week near Tehran. All 176 people on board were killed.

"As soon as we have detailed information, we will decide if and when our Iranian flights can be operated again," Lufthansa said in a statement.

Some Western leaders say the plane appeared to have been unintentionally hit by a surface-to-air missile amid tensions between the U.S. and Iran. Iranian officials have ruled out a missile attack.

1:40 p.m.

The French air accident investigation authority says it has been invited by Iran to join the probe into this week's plane crash near Tehran.

The French authority known by its French acronym BEA said Friday it has been notified by Iran's air accident board. The BEA in a Twitter post says it has designated an accredited representative to the investigation.

The plane's engine was designed by CFM International, a joint company between French group Safran and US group GE Aviation.

French Foreign Minister Jean-Yves Le Drian earlier Friday told RTL radio that "it is necessary to establish the truth" and called for "total clarity." He wouldn't comment on whether the plane could have been hit by an Iranian missile, which the U.S. has asserted.

1:20 p.m.

Sweden's Prime Minister Stefan Lofven says the information that the plane that crashed in Iran this week could have been hit by a missile is "very serious." At least 10 Swedes were on board.

Lofven told The Associated Press in an email Friday that he and Canadian Prime Minister Justin Trudeau spoke and agreed that "this information would further increase the need for an urgent, complete and transparent investigation."

Canada is among the countries saying a missile could have struck the plane that crashed near Tehran and killed all 176 on board, including dozens of Canadians.

The Swedish leader also said he and Trudeau agreed that "the affected countries need to be able to contribute national expertise as well as provide full transparency in the investigation."

Lofven also has spoken with Ukraine's president.

12:50 p.m.

German Foreign Minister Heiko Maas says if it's confirmed that the jetliner that crashed in Iran this week was mistakenly shot down by an air defense missile "then one is honestly left lost for words."

Maas also told German broadcaster n-tv that Berlin told Tehran on Thursday it expects other nations to be involved in the investigation.

"The greatest possible transparency (is needed) for total clarity and so nothing is swept under the carpet, because that would really not be conscionable given the dimension," he said.

He said Iran's invitation to the Americans to help investigate is "a very important signal" and he added that "I think all sides have recognized that the time has passed now for military escalation, that it makes sense to talk to each other."

12:30 p.m.

France is offering to help Iran investigate this week's crash of a Ukrainian airliner that killed all 176 people on board.

French Foreign Minister Jean-Yves Le Drian said Friday on RTL radio that "it is necessary to establish the truth" and called for "total clarity." He wouldn't comment on whether the plane could have been hit by an Iranian missile, which the U.S. has asserted.

He said France is available to offer expertise. French air accident investigators have extensive experience with international crashes because they are involved any time an Airbus has an accident. This week's crash involved a Boeing.

Le Drian also insisted that the Iran nuclear deal "is not dead." Le Drian is meeting Friday with other European diplomats to discuss the deal on curbing Iran's nuclear activities after Tehran said it would no longer abide by any limitation to its enrichment activities.

12:10 p.m.

The head of Iran's investigation team into the plane crash this week that killed all 176 people on board tells state television that Tehran will use expert help from Russia, Ukraine, France and Canada "if we cannot recover data" from the plane's recorders.

Hassan Rezaeifar said Friday that recovering the data could take more than one month and the entire investigation into the crash could take more than one year.

He also said the flight had been delayed by about an hour because the pilot decided to unload part of the luggage as the flight was overweight.

Western leaders have said the plane appeared to have been unintentionally hit by a surface-to-air missile near Tehran, but Iranian officials have ruled out a missile attack.

11:55 a.m.

Russian lawmakers say statements about a missile hitting a Ukrainian jetliner that crashed this week in Iran are "groundless" and they accuse the West of prematurely assigning blame to Tehran. All 176 people on board the plane bound for Ukraine died.

Vladimir Dzhabarov, a lawmaker with Russia's upper house of parliament, said Friday that "we need to be cautious with conclusions. Iranians have invited Ukraine to take part in the investigation. Why would they do it if they knew they had shot (the plane) down?"

Leonid Slutsky, a lawmaker with Russia's lower house of parliament, echoed that sentiment and said conclusions about the cause of the crash could be politically motivated.

"Facts and solid evidence are needed, rather than vague references to intelligence findings. So far it has all been groundless," Slutsky said.

Western leaders have said the plane appeared to have been unintentionally hit by a surface-to-air missile near Tehran hours after Iran launched ballistic missiles at two U.S. bases in Iraq to avenge the killing of its top general in an American airstrike.

11:20 a.m.

The Ukrainian president says he is not ruling out the possibility that the plane which crashed earlier this week in Iran had been hit a by a missile.

"The missile theory is not ruled out, but it has not been confirmed yet," Volodymyr Zelenskiy said in a Facebook post Friday. All 176 people on board the plane bound for Ukraine died.

Zelenskiy reiterated his call for "all international partners" — the U.S., Britain and Canada in particular — to share data and evidence relevant to the crash.

He also announced plans to discuss the investigation with U.S. Secretary of State Mike Pompeo on Friday afternoon.

Western leaders have said the plane appeared to have been unintentionally hit by a surface-to-air missile near Tehran hours after Iran launched ballistic missiles at two U.S. bases in Iraq to avenge the killing of its top general in an American airstrike.

Iranian officials have ruled out a missile attack but have invited the U.S. accident-investigating agency to take part in the investigation.

10:10 a.m.

Iranian authorities have given Ukrainian investigators access to the fragments of the plane that crashed earlier this week and they were examined late Thursday, according to a statement by the Ukrainian president's office.

"It is too early on in the investigation to reveal specific details," the statement says.

The president's office also says DNA is being collected from relatives of Ukrainians who died in the crash in order to identify the bodies.

Iran has invited Boeing to take part in the investigation into the Ukrainian jetliner that crashed and killed all 176 people on board, state media reported Friday.

9 a.m.

Iran has invited Boeing to take part in the investigation into a Ukrainian jetliner that crashed earlier this week at a time of soaring tensions between Washington and Tehran, killing all 176 people on board, state media reported Friday.

The move came after Western leaders said the plane appeared to have been unintentionally hit by a surface-to-air missile near Tehran hours after Iran launched ballistic missiles at two U.S. bases in Iraq to avenge the killing of its top general in an American airstrike.