Californian and Irish Students Killed in Berkeley Balcony Collapse Authorities are working to figure out what caused the balcony to collapse.

 -- The students killed in a Berkeley, California balcony collapse have been identified as a group of students, including five from Ireland in what officials from the nation called a "national tragedy."

"We have thousands of Irish students come to the US every summer. ... To have this happen at the start of this season is something that has left us all frozen in shock and in disbelief," said Phillip Grant, the consul-general of Ireland.

Authorities said they were still trying to figure out what caused the collapse early Tuesday morning that also left seven people seriously injured. The injured were reportedly being treated at Eden, Highland and John Muir hospitals.

"From some of the officers I spoke with, they told me that it was quite disturbing," said Berkeley Police Department Officer Byron White. "Any time you have a tragedy like this involving young people, it's disturbing. ... You hear just goes out to the families."

Officials said that five students were from Ireland -- Olivia Burke, Eoghan Culligan, Niccolai Schuster, Lorcan Miller, and Eimear Walsh, all 21.

Owen Buckley, 21, a student at Dublin State University, said he knew one girl who'd attended the girl. Buckley said she'd been injured and hospitalized.

"It was just a loud crash," said Buckley, who was not at the party and in his unit on the third floor, "and then silence for a couple of minutes and then just a scream."

"We were sure someone was shot," he said.

All were on J-1 student visas and participating in a student exchange summer work program. Most were from South Dublin and attended various schools.

"My heart goes out to the families and loved ones of the deceased and those who have been injured in this appalling accident," Ireland's Minister for Foreign Affairs and Trade Charlie Flanagan said in the statement.

Ashley Donohoe, 22, of Rohnert Park, California, was also killed in the incident.

Witnesses said the group was celebrating a 21st birthday when the balcony, located on the fourth floor of the building, on Kittredge Street, collapsed around 12:41 a.m.

"I just heard a bang and a lot of shouting," Dan Sullivan, a 21-year-old student from Ireland, told The Associated Press.

Authorities are working with building inspectors to figure out what caused the collapse, police said.

According to officials, the building was under construction from 2005 to 2007. A final inspection was made in January 2007, but the results were not immediately clear.

Three apartments in the building with similar balconies were "red-tagged" officials said, which forbids access to the area.

According to officials, the building was subject to the 1998 building code, which meant that balconies had to be able to withstand 60 pounds per square foot of pressure. It was not clear how much pressure was being exerted when the balcony collapsed.

Police Chief Michael Meehan said the department had received a noise complaint about the building but it was given a lower priority because of a call of shots fired elsewhere. When police did respond to the call for the balcony collapse, they arrived within 2 minutes, the chief said.

Greystar Management, which oversees the building, expressed its condolences in a statement.

"As the property management company, we have taken precautionary steps to limit access to other balconies at the apartment complex as law enforcement completes its investigation," a rep for the company said in a statement. "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."

The Associated Press contributed to this report.