Police said 20-month-old Nevaeh Bryant of Derby, Conn., was visiting her relative Friday in West Haven when she was attacked by two or three dogs.
She died at Yale-New Haven Hospital.
Lt. Robert Proto said Saturday the dogs had been put in another room but somehow got out.
He said that because of the severity of the attack and the aggressiveness of the dogs, the animals were euthanized.
Police believe they were pit bulls.
The aunt told the New Haven Register the dogs had never before been aggressive.
She asked for prayers for the girl and the girl's family. The paper did not identify her.
Proto said a decision regarding charges has not yet been made.