TSA officers caught this loaded handgun at the Portland International Jetport checkpoint on Thursday. Credit: Courtesy of the Transportation Security Administration

A Florida man was detained on Thursday after he allegedly brought a loaded gun into Portland International Jetport.

The man, who was not identified, had a 9 mm handgun loaded with 12 bullets, including one in the chamber, in his knapsack when he attempted to pass through a checkpoint at the Portland airport, according to Lisa Farbstein, a spokeswoman for the Transportation Security Administration.

The gun was found when his knapsack passed through the checkpoint X-ray machine, and TSA officials alerted airport police, who detained the man for questioning, Farbstein said.

This is the second time this week that TSA has detected a loaded firearm at a checkpoint at the Portland airport. On Wednesday, a Minot woman, who the TSA also did not identify, was caught with a loaded 9 mm handgun tucked into her purse. Those are the only two firearms detected at the jetport so far this year.

In 2018, 4,239 firearms were discovered in carry-on bags at airport checkpoints across the country, up from 3,957 the year before, according to the TSA. Nearly 90 percent of those were loaded, while a third had a bullet in the chamber.

Passengers are permitted to travel with firearms in checked baggage if they are unloaded, packed in a hard-sided case, locked and packed separately from ammunition. Anyone who brings an undeclared firearm through a checkpoint can face criminal charges and civil penalties up to $13,333, according to the TSA. A typical first offense for carrying a handgun into a checkpoint is $4,100.