Screeners with the Transportation Security Administration seized four guns at the Portland International Jetport passenger screening area last year, the same number seized the year before.

Boston, by comparison, had 10 guns seized at checkpoints in 2015, up from six the previous year.

“In the vast majority of cases passengers claim to have forgotten where they placed their firearms,” said Michael McCarthy, spokesman for the TSA. “In every case TSA requests a response from local law enforcement who responds to the checkpoint to take possession of the firearm and to interview the passenger.”

The TSA can impose civil penalties ranging from $1,500 to $7,000 for bringing a gun to a security checkpoint.

McCarthy said he was able to locate details about two of the incidents:

• A 74-year-old woman traveling from Portland to Atlanta on Jan. 22, 2015, was found to have a 9-mm Ruger handgun with 10 rounds, one of them chambered.

• On April 20, a 67-year-old man flying to Atlanta had a .22-caliber Derringer with five rounds, one of them chambered.

Guns, like other weapons, are not allowed in carry-on luggage. They can be put in checked baggage as long as they are unloaded, packed safely and the declared to the airline, the agency said.

Nationally, the TSA intercepted 2,653 guns in carry-on bags at airport security checkpoints in 2015, 83 percent of which were loaded. That was 20 percent more than the 2,212 guns found in 2014, the agency said in a press release.

The airports with the most guns seized last year were Dallas/Fort Worth International Airport with 153, Hartsfield-Jackson Atlanta Interntional Airport with 144 and George Bush Intercontinental Airport in Houston with 100.

The release also noted that TSA screened 708 million passengers and 1.6 billion carry-on bags.

The release also said that nationwide, 98 percent of passengers waited less than 20 minutes in line at a security checkpoint.