Police Commissioner Ray Kelly said Thursday that investigators are looking into whether Officer Michael Pena, who is accused of raping a Manhattan school teacher, may have been involved in other unsolved sex attacks.

Pena was off-duty when he was arrested last week for allegedly raping a woman on her way to work in Inwood.

Prosecutors say Pena was drunk when he showed the accuser a gun, then pulled her into a backyard.

Kelly said the brazenness of the attack could suggest that Pena committed other sex crimes.

"We asked that question of the psychologist, and they believe that it certainly is possible that something else happened in the past, that it was not the first time,” said Kelly. “But so far we can't say with any sort of certitude that there's another incident."

Kelly said investigators focused on several cases that Pena could have been involved in.

Pena is being held on $1 million bond.