AKIPRESS.COM - A 21st-birthday party thrown by a group of visiting Irish college students turned tragic early Tuesday when the fifth-floor balcony they were crammed onto collapsed with a sharp crack, spilling them about 50 feet onto the pavement.

Six people were killed and seven seriously injured.

Officials were working to figure out why the small balcony broke loose from the stucco apartment building a couple of blocks from the campus of the University of California, Berkeley.

But one structural engineer said it may have been overloaded if, as city officials said, it was holding 13 people.

Five of the dead were 21-year-olds from Ireland who were in the country on J-1 visas that enable young people to work and travel in the U.S. over the summer, while the sixth victim was from California, authorities said.

The accident brought an outpouring of grief in Ireland from the prime minister on down, with the country's consul general in San Francisco calling it a "national tragedy," the U.S. media report Wednesday.