Specialists investigating the balcony collapse at University of California’s Berkeley campus that killed six people and injured seven others say water damage may have caused the structure to give way.

The balcony collapse happened during a 21st birthday party in the early hours of June 16.

Authorities said 13 people were on the fourth-floor balcony when it collapsed.

The victims were mostly Irish students who were living temporarily in the US as part of a work exchange program.

An initial investigation found that the balcony support’s wooden beams may not have been sealed properly at the time of construction, Berkeley Mayor Tom Bates said.

The mayor said: “More than likely, it was caused by rain and water damage.”

However, Tom Bates later stressed that this was not an official conclusion and that an investigation was still under way.

Building inspectors also ordered that two other balconies at the Library Gardens apartment building be demolished, saying they were unsafe and could collapse.

A former city official familiar with the apartment complex told the San Francisco Chronicle that the 5ft by 10ft balcony was “decorative” and not designed to hold a large number of people.

“This was meant just to be a place where someone could stand out for bit,” Carrie Olson told the publication.

“Not for something like 13 people.”

People left flowers and other tributes at the scene on June 17 as flags on both sides of the Atlantic flew at half-mast.

A memorial service was planned for June 17 in nearby Oakland, with victims’ relatives travelling from the Irish Republic to California.

Meanwhile, many in the Irish Republic and the US criticized coverage of the story in the New York Times, accusing the newspaper of “victim-blaming”.

The New York Times wrote a story about the work-visa program that some of the victims were on, mentioning “a series of high-profile episodes involving drunken partying and the wrecking of apartments”.

The newspaper’s public editor said in a blog that many of the complaints were valid. New York Times spokesperson Eileen Murphy said in an email: “It was never our intention to blame the victims and we apologize if the piece left that impression.”