The death toll stands at six in the early Tuesday collapse of a fourth-storey balcony that killed and injured Irish students in Berkeley, California, according to the local coroner's office, dpa reported. The students were apparently celebrating a 21st birthday of one of their number. A person in the coroner's office said he could not confirm the national identity of the dead, and told dpa that he could not share information about the injured and dead until families are notified. In Dublin, Irish Prime Minister Enda Kenny told Parliament that, based on information from California police, there were 13 people on the balcony at the time of the collapse. Kenny said "current information suggests all of those are Irish," Britain's PA Press Association reported. "My heart breaks for the parents who lost children this morning and I can only imagine the fear in the hearts of other parents whose children are in California this summer as they seek to contact them now," he said. There were no immediate details of how the incident occurred. Police are investigating the cause for the collapse at the Library Gardens apartment complex, which was built in 2006. Pictures have shown the fourth-story balcony to have broken off from the building. Part landed on the third-floor balcony below and part landed in the street. Irish Foreign Affairs Minister Charlie Flanagan confirmed that the Irish students were in the US for the summer on J1 visas, a non-immigrant document issued to participants in exchange programmes. He said that the accident occurred during a 21st birthday celebration. "It's an appalling tragedy, an appalling loss of life for young people whose hopes and dreams of the future have suddenly and without notice been shattered," he said. Hospitals at Berkeley and nearby Oakland and Walnut Creek were treating the injured while several fire crews responded to the collapse, news reports said. The foreign ministry said the Irish consul in San Francisco was in close contact with US authorities. Alamada County, where the incident happened, plans to hold a press conference once all the families of those killed and injured have been notified.