Authorities were investigating who owned the gun and how it got in the men's room trash can at Tucson International Airport, Transportation Security Administration spokesman Christopher White.

Nearly 300 passengers were evacuated from the concourse for about a half-hour while the area was searched by TSA and airport security officers with canine teams, officials said. Five outbound flights were delayed, the longest for 64 minutes.

Paula Winn, an airport spokeswoman, said she did not know who found the weapon, and officials had no immediate explanation for how someone could have gotten a loaded handgun beyond the security screening area.

"It's a matter that's under investigation," said TSA spokesman Nico Melendez in Los Angeles. "I would not be able to speculate right now.'