Six people have been killed, and seven others have been seriously injured, when a fourth-floor balcony in California gave way.
At least five of the dead are believed to be young people from Ireland.
Police found debris on the street below after an emergency call at 01:00 local time (08:00 GMT) in Berkeley.
The victims are believed to have been holding a 21st birthday party at the time, Irish officials said, but the cause of collapse is unknown.
They are believed to have been in the US on temporary worker visas.
Photos taken at the scene appear to show a balcony on the fourth floor of the building fallen to the balcony on the level below.
Enda Kenny, the Irish Prime Minister, has said that police told him there were 13 people on the balcony when it collapsed.
Irish Foreign Minister Charlie Flanagan said that four of the victims died at the scene and another died in hospital.
The Alameda County coroner’s office later told the BBC a sixth person had died in hospital.
The balcony, which is approximately 5 feet (1.5m) long and 10 feet wide, broke from the building around 00:41 local time.
Berkeley Police spokesman Byron White said first responders described the scene as “quite disturbing”.
Many of those hurt have life-threatening injuries, said Jennifer Coats, a Berkeley Police Department spokeswoman.
Police received a complaint about loud noise at the flat about an hour before the balcony collapsed, but did not go to the building to investigate, they said.