BERKELEY, CALIF (TIP): A 21st-birthday party thrown by a group of visiting Irish college students turned tragic early June 15 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.

Police and fire and building officials were working to figure out why the small balcony broke loose from the side of the stucco apartment house 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.

High school student Jason Biswas’ family nearby was awakened by the noise.

“They thought there was an earthquake, but then we looked out the window and saw seven or eight people on the ground,” the 16-year-old said. “There were piles of blood everywhere.”

Five of the dead were 21-year-olds from Ireland who were in the country on so-called 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 news 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.”

Police had gotten a complaint about a loud party in the apartment about an hour before the accident but had not yet arrived when the balcony gave way just after 12:30 a.m., spokesman Byron White said.

“I just heard a bang and a lot of shouting,” said Dan Sullivan, a 21-year-old student from Ireland who was asleep in the five-story building. Mark Neville, another Irish student in the building, said: “I walked out and I saw rubble on the street and a bunch of Irish students crying.”

The U.S. government’s J-1 program brings 100,000 college students to this country every year, many of them landing jobs at resorts, summer camps and other attractions. The San Francisco Bay area is especially popular with Irish students, about 700 of whom are working and playing in the region this summer, according to Ireland’s Consul General Philip Grant. Many work at Fisherman’s Wharf and other tourist sites.

Sinead Loftus, 21, who attends Trinity College Dublin and is living this summer in a different apartment in Berkeley, said Berkeley is “the Irish hub.” In fact, she said, “I’ve heard people complain there are too many people from Ireland here.”

“It’s student-friendly, it’s warm and it’s a lot cheaper than San Francisco,” she said.

Berkeley Police Chief Michael Neeham said the response to the noise complaint had been given a lower priority after police received a call of shots fired elsewhere.

Police arrived to find the metal-rail balcony had fallen off the side of the building and landed on the fourth-floor balcony beneath it. The pavement was strewn with rubble and the red plastic cups that are standard at practically every college party.

Investigators will probably look at such things as whether the balcony was built to code, whether it was overloaded and whether rain or other weather weakened it, said Kevin Moore, a San Francisco-based engineer and chairman of the structural standards committee of the Structural Engineers Association of California.

Berkeley officials said the building code would have required the balcony to hold at least 60 pounds per square foot. Its exact dimensions were not released, but Grace Kang, a structural engineer and spokeswoman for Pacific Earthquake Engineering Research Center at Berkeley, said it looked to her to be 4 by 6 feet, or 24 square feet. That would mean it was supposed to hold at least 1,440 pounds.