Investigations have been launched against more than 600 people in relation to buildings that collapsed in Turkey’s catastrophic earthquake earlier this month, a government official said Saturday.

Justice Minister Bekir Bozdag said 184 of the 612 suspects had been jailed pending trial. Those in custody include construction contractors and building owners or managers, he said in televised comments from a coordination center in Diyarbakir in southeast Turkey.

“The detection of evidence in the buildings continues as a basis for criminal investigation,” Bozdag added.

The aftermath of the 7.8-magnitude quake on Feb. 6, which led to nearly 48,000 deaths in southern Turkey and northern Syria, has seen Turks question the structural integrity of many of the 173,000 buildings that collapsed or were seriously damaged.

Also Read: Death toll from Turkey, Syria earthquake tops 47,000

Experts have said many toppled structures were built with inferior materials and methods and often did not comply with government standards. Opposition parties have accused President Recep Tayyip Erdogan’s administration of failing to enforce building regulations.

The mayor of a town close to the epicenter of the earthquake was detained as part of an investigation into collapsed buildings, the Cumhuriyet newspaper and other outlets reported Saturday.

Okkes Kavak, who heads the district of Nurdagi in Gaziantep province and is a member of Erdogan’s Justice and Development Party (AKP), is said to have failed to ensure construction inspections were carried out.

AFAD, Turkey’s disaster management agency, said that 9,470 aftershocks had hit the region affected by the quake.

“This will continue for a long time… we expect these aftershocks to last for at least two years,” AFAD General Manager Orhan Tatar said in a media briefing in Ankara. He said a 5.3-magnitude quake that hit Bor, a town around 150 miles (about 245 kilometers) west of the Feb. 6 epicenter, was considered “independent” of earlier temblors.