Perth, Sep 10 (AP/UNB)— Three children, their mother and grandmother have been found dead in a house in the Australian city of Perth after a man alerted police, detectives said Monday.

The children were twin girls aged 2 and their 3-year-old sister, a police statement said. Police have not said how the five died. A man aged in his 20s alerted police on Sunday morning.

"The man currently assisting police remains in custody," a police statement said, adding "no charges have been laid at this time."

Homicide detectives and specialist forensic police will continue to comb the address in the suburb of Bedford for evidence and clues to what happened.

"That will take a period of time and it could be a number of days," Assistant Police Commissioner Paul Steel said.

"It is a tragic thing when incidents like this occur. It does send a ripple through the community of Western Australia," Steele said.