A loaded and undeclared .38-caliber handgun tumbled from a checked bag at Los Angeles International Airport Sunday, prompting police to detain the gun owner temporarily.

A luggage ramp crew discovered the weapon after it fell from an unzipped compartment in a duffel bag they were loading onto Alaska Airlines Flight 563, according to police and the airlines. The plane was leaving the terminal at 8:15 a.m. Sunday, bound for Portland, Ore.

Workers called Los Angeles Airport Police to report the discovery. The owner of the gun, whose name has not been released, was questioned at the Los Angeles Police Department's Pacific station and was allowed to board a later flight to Portland. The gun was turned over to Los Angeles police, the sources said.

Guns are allowed in locked containers in checked bags, but they are not allowed to be loaded, and passengers are required to notify the airline. The traveler hadn't done that, according to the Transportation Security Administration and Alaska Airlines.

The traveler told authorities he had flown out of Portland with the same bag, with the gun inside, three days earlier. It was not clear whether he had notified the airline about the gun that time.

TSA spokeswoman Lorie Dankers said the bag had been screened for explosives and none was found. She also noted that because the firearm was in a checked bag, the passenger would not have had access to it during the flight. Dankers said the TSA screens for firearms stowed in carry-on luggage but that it was not the agency's responsibility to detect firearms in checked luggage.

Alaska Airlines spokeswoman Bobbie Egan said airline personnel do not screen luggage and that it is passengers' responsibility to "self-disclose dangerous goods." They are prompted to do so when they check in, she added.

Although representatives of both the TSA and the airline said they were following established policies, Marshall McClain, the president of the union that represents officers in the Los Angeles Airport Police, said the TSA should more thoroughly screen luggage.

"Local law enforcement needs to know that TSA is doing their part," McClain said.