Baggage handler trapped in cargo hold during flight

United Airlines is investigating how a baggage handler became locked in the cargo hold of a plane and remained trapped during an hourlong flight.

In a statement, the airline said the man was found unharmed after United Airlines Flight 6060 landed at Washington Dulles International Airport on a New Year's Day flight from Charlotte Douglas International Airport.

During the flight, the plane reached an altitude of 27,000 feet, according to CNN affiliate WBTV-TV in Charlotte, North Carolina.

Radio traffic revealed that workers initially treated the incident as a security issue, the CNN affiliate reported.

"We're going to work it as a security incident until we can get some confirmation to who he is even though he's in trade dress for a ramper in Charlotte. The flight crew doesn't remember seeing him or anything like that," radio traffic said, according to the TV station.

An airline representative told CNN that a vendor for United employs the baggage handler. The airline didn't release the handler's name.