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(Reuters) - No criminal charges will be filed in connection with the deadly collapse of an apartment balcony in Berkeley, California, last year in which five visiting Irish students and an American friend were killed, prosecutors said on Tuesday.

An investigation showed dry rot caused the balcony to give way during a birthday party in June, and the building’s maintenance and construction crews “likely” bore some responsibility, Alameda County District Attorney Nancy O’Malley said.

But O’Malley said there was not enough evidence to prove reckless disregard for human life that would be needed for a charge of criminal manslaughter.

“This is not a decision that I came to lightly,” O’Malley said in a statement.

Thirteen people were crowded onto the balcony when it ripped away and spilled everyone 40 feet (12 meters) to the street.

The young people attending the party were mostly college students from Ireland working in the San Francisco Bay area for the summer on temporary visas.

Civil lawsuits were filed last year on behalf of seven survivors and the families of five students who died, including against the building’s owner, a BlackRock Inc-managed real estate fund.