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Six people died and seven others were wounded when a fourth-floor balcony collapsed early Tuesday in Berkeley, California, according to authorities.

Authorities identified the dead as three women and three men, and said five of those killed were Irish students visiting on temporary work visas.

The Irish students killed were identified as Olivia Burke, 21; Eoghan Culligan, 21; Niccolai Schuster, 21; Lorcan Miller, 21; and Eimear Walsh, 21. A sixth victim, Ashley Donohoe, 22, was from California.

Related: Berkeley Balcony Collapse — Frantic 911 Audio Released

Ireland sends around 8,000 students to the United States each year under the J-1 visa program, said Philip Grant, Consul General of Ireland for the Western United States, and the visits are often a formative experience.

"To have this happen at the start of the season is something that has left us all frozen in shock and in disbelief," Grant said.

Damage is seen at the scene of a 4th-story apartment building balcony collapse in Berkeley, California June 16, 2015. ELIJAH NOUVELAGE / Reuters

Police were unable to confirm what sort of gathering was taking place at the apartment, saying only that a call came in just before 1 a.m. (4 a.m. ET) about a balcony collapse. Two women at the scene told NBC Bay Area that a number of people were gathered in the apartment for a 21st birthday party.

Thirteen people fell from the balcony and four were pronounced dead at the scene, according to Berkeley Police spokesman Bryon White. One person died at the hospital, White said. A second person died later Tuesday morning, according to the Alameda County Coroner’s Office.

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Another seven were being treated for serious injuries, according to police. Most of the Irish students killed in the collapse were from South Dublin, Grant said.

Berkeley Police Chief Michael Meehan said police received a call of a loud party at 12:02 a.m., but did not respond because other reports of unrelated shots fired in another part of the city took priority. The balcony collapsed at around 12:40 a.m., he said.

"At this point, we still have no indication of criminal activity or a criminal intent," Meehan said. Even if police had responded to the noise complaint, they would not have entered the apartment or inspected the balcony, he said.

Authorities were working to determine what caused the collapse. Officials said inspectors are looking at the property and three other similar balconies on the building were ordered closed. The building was built in 2007.

Earlier, Berkeley Police spokeswoman Jennifer Coats told NBC News the balcony fell to the sidewalk from the top of a four-story building. She said Berkeley Fire Department and city officials responded to the scene and had secured the area around the collapse.

The building where the collapse occurred is just two blocks from the campus of the University of California, Berkeley, according to NBC Bay Area. UC Berkeley said in a tweet that none of the victims were students at the school. Students were planning to gather at a sports bar to remember the victims.

Greystar, the company that manages the Library Gardens apartment complex where the collapse occurred, said in a statement that, "our hearts go out to the families and friends of the deceased and those injured in this tragic accident." It said it has limited access to all other balconies and has called in an independent structural engineer to determine the cause of the collapse.

Neighbor Gerald Robinson said he didn’t know the people who lived in the apartment, but he took two people to the hospital after “desperate students” needed a ride. He told NBC Bay Area that the victims were unaware of the deaths at the time.

"The kids there have no idea what's happened," he said.

This man says he gave a young couple ride to Highland Hospital,said there was party on 4th flr when balcony collapsed pic.twitter.com/fc4PjtQS79 — Stephanie Chuang (@StephChuang) June 16, 2015

Ireland’s minister of foreign affairs, Charles Flanagan, said said in a statement that Ireland's consul general in San Francisco was in touch with authorities and providing assistance to those affected.

"It’s every parent’s worst nightmare," he said.

University College Dublin said President Andrew Deeks expressed his condolences to the families affected.

"It is heart-breaking to imagine that such a tragedy would strike these wonderful students when their lives are opening up to discover the world," he said. The university did not confirm whether any of its students was among the dead.

The two Irish travel companies that work with the U.S. State Department's J-1 visa program, which allows international students to work in the U.S. for up to four months, said they were working with the Irish government to respond to the deadly incident. "This is a devastating experience for everyone," said a statement from the travel agencies, USIT and SAYIT.

Irish President Michael D. Higgins got word of the incident while on a trip to Italy. “My heart goes out to the families and loved one’s of all those involved,” he said in a statement.

Ireland’s U.S. ambassador Kevin O'Malley offered condolences to the victims and their families. “All of us at the United States Embassy are greatly saddened by news of this tragic incident and are ready to do whatever we can to assist the Irish Department of Foreign Affairs at this difficult time,” O'Malley said in a statement.

The Union of Students in Ireland (USI) said it was “shocked and deeply saddened” by the loss of life. “'The thoughts and sympathies of the whole student movement in Ireland are today with the families and friends of those young people caught up in this terrible event,” said USI president Laura Harmon.