SAN FRANCISCO -- A controversy simmered Thursday over the police investigation into a New Year's Eve attack on a Yale University singing group that left one member with a broken jaw and another with a concussion.

Police Chief Heather Fong has defended the actions of her officers, telling the San Franciscp Chronicle that no arrests were made at the time of the attack because officers were unable to find anyone who could substantiate any charges.

"When the facts are there and we have individuals providing information specifically saying this person did this, then we ... act," Fong told the paper. "But those individuals weren't there for the officers to interview."

However, members of the choir have told friends and relatives that they pointed out the individuals whom attacked them and were told by police to leave.

Appearing On KTVU Mornings On 2, former San Francisco prosecutor Jim Hammer -- an attorney for one of the injured choir members -- said the party where the attack took place was being held for members of Yale's Baker's Dozen during their West Coast appearances.

"They were the guests of honor at the party (held at the home of a San Francisco police sergeant and her husband)," Hammer said. "During this party, some uninvited guests came in and that's when the trouble began."

Members of the all-male singing group were taunted with anti-gay slurs after singing "The Star Stangled Banner."

"There were some words exchanged…some (members) were violently assaulted," Hammer said. "The Yale kids rather than fight back -- cooled things down -- and left the party. That's when it got really ugly outside."

At least three members of the Baker's Dozen a cappella group were hurt. One member of the group suffered a broken jaw and another was left with a concussion.

"That's how vicious and serious this was," Hammer said. "You kick people in the head, you can kill someone."

Sharyar Aziz Jr., an 18-year-old Baker's Dozen member whose jaw was broken, said slurs were hurled at the group by their attackers.

"You're not welcome here," Aziz Jr. quoted one partygoer as saying. "He called a few members of the group, whether it was fag or homo, very, I would say, juvenile taunting."

Reno Rapagnani, a retired San Francisco police officer whose daughter hosted the event, shut down the party. As the singers headed back to a nearby home where they were staying, another group of young men got out of a van and jumped them, according to Rapagnani.

"They were surrounded, then tripped -- and when they were on the ground, they were kicked," Rapagnani said.

Two other Yale students needed medical treatment following the fight, one for a concussion and the other for cuts and a swollen ankle.

Police said they arrived and found about 20 people fighting in the street. They interviewed some of the participants but let them go after taking their names.