The balcony collapse that killed six students appears to have been caused by rotted wooden beams, Berkeley's mayor has said as the victims' heartbroken loved ones began arriving in the US from Ireland.
Mayor Tom Bates said investigators believe the wood was not caulked and sealed properly at the time of construction and was damaged by moisture as a result.
The crowded fifth-floor balcony broke off an apartment building during a 21st-birthday party held by visiting Irish students yesterday, spilling 13 people 50 feet onto the pavement below. In addition to the six killed, seven were seriously hurt.
"More than likely, it was caused by rain and water damage that was caused to the support beams," Mr Bates said. He said it was "obviously a bad idea" for 13 people to crowd onto such a small balcony but added that he is not blaming the victims.
Cassandra Bujarski, a spokeswoman for the apartments' property management firm, Greystar, had no comment.
Building inspectors also determined another balcony at the Library Gardens apartment complex was "structurally unsafe and presented a collapse hazard", and ordered it to be demolished.
Two other balconies were red-tagged, or declared off-limits, at the apartments, which were completed in 2007 and are popular among visiting students and those at the nearby University of California, Berkeley.
Across the Atlantic, flags flew at half-staff around Ireland and the country's parliament suspended normal business as the nation mourned the dead: Ashley Donohoe, 22, of Rohnert Park, California, and Olivia Burke, Eoghan Culligan, Niccolai Schuster, Lorcan Miller and Eimear Walsh, all 21-year-olds from Ireland.
"They were in the prime of their lives," said Bernadette Prendiville, principal of the high school from which Ms Burke and Ms Walsh graduated. "They had a successful time in school, went about their work quietly and had everything going for them, everything ahead of them."
Josh Wilson, assistant principal at Rancho Cotate High School, said Ms Donohoe was a remarkably well-liked and cheerful young woman who returned after graduating to help coach the football team.
"She just always had a smile on her face and transcended peer groups and cliques and had a friend in just about every social circle," he said.
A Mass was planned for this evening in Oakland for the victims, and grieving family members made their way toward Berkeley from Ireland.
The Irish students were working and travelling in the US over the summer, a rite of passage enjoyed by thousands of their countrymen.
"For many of my countrymen, this is a favourite experience, and to have this happen at the start of the season has left us frozen in shock," said Philip Grant, Ireland's San Francisco-based consul general.
The Rev Aidan McAleenan, a Roman Catholic priest who was sitting with two of the injured at John Muir Medical Center in Walnut Creek, said that they were doing fine but that friends of the dead and injured were in shock and having a hard time talking.
Darrick Hom, president of the Structural Engineers Association of Northern California, visited the site of the collapse and said he noticed the broken wooden beams under the balcony were crumbling in the hands of investigating engineers.
"That wood was decayed or had some serious deterioration to the point where they could touch it with their hands and it was coming off in chunks in their hands," Mr Hom said. He said it was surprising to see such deterioration in a building just eight years old.
Normally, any building material - wood, steel or concrete - that will be exposed to the elements requires weatherproofing at the time of construction, Mr Hom said.
Nothing in state code requires follow-up inspections of balconies after a building is issued a certificate of occupancy, unless there is major remodelling, said Brian Ferguson, deputy director of the state Department of General Services.
Although Florida has some balcony inspection requirements, most places do not require any reviews after construction is complete. Lawrence Ubell, president of New York-based Accurate Building Inspectors, said that could spell trouble.
"Annual inspections are so important for all balconies and terraces, but particularly for ones made of wood," he said. "In fact, rotting wood is the biggest cause of balcony and terrace failures."
Sari Kosdon, a Berkeley graduate student who has lived at Library Gardens since last August, said she feels terrible about the Irish students' deaths.
"I see these kids all the time and they are just so happy to have gone to this country and the opportunity," she said. "I feel like as a country we've failed them."