Canine teams searched two terminals at Baltimore/Washington International Thurgood Marshall Airport Friday morning after screeners discovered a firearm in a carry-on at a security checkpoint.

Police said there was no indication it was a terrorism incident.

Authorities held onto the carry-on, but its owner continued through the checkpoint and disappeared, prompting Maryland Transportation Authority police to evacuate concourses A and B, said BWI spokesman Jonathan Dean. Those concourses serve one of the airport's largest carriers, Southwest Airlines, Dean said.

"We simply were acting with all due precaution, the item is being held," Dean said.

The recovered gun was a .25 caliber semiautomatic pistol manufactured by Raven Arms, said Transportation Security Administration police spokesman Jonathan Green.

Police and security personnel searched without success for a man in his early 30s dressed in blue jeans and a red and black sweat suit track jacket, Green said.

The concourses were reopened about 90 minutes after the 6:40 a.m. incident and all passengers were being required to go through screening again.

"There is no indication that this was a terrorism incident," Green said. "It appears to just be a traveler with a handgun in his luggage, but we won't know for certain until we find the guy," Dean said.

The incident caused more than a dozen morning flight delays, said Cheryl Stewart, an airport spokeswoman.