A small monkey stashed in a man's hat during a flight to New York has died, but federal health authorities don't know why.

The fist-sized tamarin showed no signs of illness during a quarantine period, Federal Centers for Disease Control and Prevention spokeswoman Shelly Diaz said Wednesday. The agency had lifted the quarantine and was trying to find the animal a permanent home when it died, she said.

The primate was seized as its owner got off a plane at LaGuardia Airport on Aug. 7. It apparently escaped detection during a flight from Lima, Peru, and a stopover in Fort Lauderdale, Fla. The forest-dwelling creature was spotted after it crept out and perched on its owner's ponytail during the flight to New York.

The owner was questioned and released. He told authorities he didn't realize the monkey's voyage was illegal.