COPENHAGEN, Denmark (AP) — All five people inside a construction site elevator that crashed to the ground in Stockholm have died, a Swedish prosecutor said Tuesday.

Authorities had previously only reported that the occupants were seriously injured when the elevator plummeted 20 meters (66 feet) in Sundbyberg, a Stockholm suburb, on Monday. It is still unclear what caused the accident. Construction at the site has been stopped.

Gunnar Jonasson, the senior prosecutor in charge, said there is an ongoing preliminary investigation, including by the National Accident Commission, on suspicion of “work environment violations causing the death of another.”

“This is a serious incident that we are now investigating,” Jonasson said. He added that authorities are working on ensuring the identity of the deceased and contact is being made with relatives.

The prosecutor said nothing more about how or when the victims died in the brief statement.

A spokesman for the company that manufactured the elevator told the Aftonbladet tabloid on Monday that that type has been used around the world for more than 20 years, and the company had never been involved in such an incident before.