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.
PHOTOS: Several killed in balcony collapse in Berkeley
Silvia Biswas, who lives on the floor below, said noise from the party was so loud, she opened her window and yelled to keep it down. When she later was awakened by what felt like an earthquake, she looked out the window and saw bodies, including a motionless young woman on the street.
"I wouldn't have screamed at them if I had known they were going to die," she said.
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."
Police had received a complaint about a loud party in the apartment about an hour before the accident but had not yet arrived when the metal-rail balcony gave way just after 12:30 a.m., spokesman Byron White said. It landed on the fourth-floor balcony just beneath it, leaving the pavement strewn with rubble and the red plastic cups that are practically standard at college parties.
The dead were identified as Ashley Donohoe, 22, of Rohnert Park, California; and Olivia Burke, Eoghan Culligan, Niccolai Schuster, Lorcan Miller and Eimear Walsh, all from Ireland. The Irish students attended various colleges in Dublin. Some worked at San Francisco's Pier 39.
Walsh and Burke were hostesses at Haza Zen, a Japanese restaurant at Pier 39, said restaurant owner Alvin Louie.
"They were great young kids, very enthusiastic, full of energy," Louis said. "We're all devastated."
The U.S. government's J-1 program brings 100,000 college students to the country every year, many landing jobs at resorts, summer camps and other attractions. About 700 of them whom are working and playing in the San Francisco Bay Area this summer, according to Ireland's Consul General Philip Grant.
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."
"It's student-friendly, it's warm and it's a lot cheaper than San Francisco," she said.
Investigators will look at things such as whether the balcony was built to code, whether it was overloaded and whether rain or other weather weakened it, said Kevin Moore, chairman of the structural standards committee of the Structural Engineers Association of California.
Balconies are exposed to the elements, "so deterioration can play a part," Moore said. Weather, "overloading, inadequate design, all these things come up in the investigations."
Berkeley spokesman Matthai Chakko said that officials have not measured the balcony to find out how big it was and how much weight it was built to bear based on the 60-pound-per-square-foot standard in place when the building went up. The city's requirement for balconies has since been raised to 100 pounds.
Chakko said there is no city requirement to post a weight restriction for balconies in apartments.
The exact dimensions of the balcony that failed were not released. Estimates varied, with Mayor Tom Bates saying city officials thought it was about 9 feet by 5 feet, while 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.
The larger estimate would mean the balcony should hold 2,850 pounds, while Kang's estimate would be half that. Kang said it appeared small for 13 people.
"They were packed like sardines, and then they were moving," Kang said. When people are moving it "may further exacerbate" the strain.
The Library Gardens apartment complex, completed in 2007, is in a lively part of downtown Berkeley close to the campus and is a popular place for students to live. Several tenants reached by telephone said it is well-maintained.
The building is owned by BlackRock, the largest asset-management fund in the U.S., according to city officials, and managed by Greystar Management, whose website says it operates more than 400,000 units in the U.S. and abroad.
In a statement, Greystar extended condolences to the victims' families and added: "The safety of our residents is our highest priority and we will be working with an independent structural engineer and local authorities to determine the cause of the accident."
On the closed street below, a shrine was growing: flowers, a pack of cigarettes, a school banner and condolence notes. Victims' relatives were expected to begin arriving from Ireland on Tuesday night.
"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," Irish Prime Minister Enda Kenny told lawmakers in Dublin.