PITTSBURGH — A Butler County man was stopped Wednesday with a loaded handgun in a backpack at Pittsburgh International Airport, authorities said.

The man, who lives in Mars, had a 9 mm pistol with 13 bullets, including one in the chamber, according to the Transportation Security Administration.

The incident marked the 29th gun found at the Pittsburgh airport security checkpoint this year. In 2018, TSA officers found 34 firearms at the checkpoint.

TSA contacted Allegheny County Police who responded, confiscated the gun and detained the man for questioning. Police did not immediately return a telephone call.

Authorities did not release the man's name because the incident remains under investigation and no charges have been filed.

TSA officials note that individuals who bring firearms to the checkpoint are subject to possible criminal charges from law enforcement.

In addition, the administration can assess civil penalties, including fines as high as $13,333 for gun violations. A typical first offense for carrying a handgun into a checkpoint is $4,100, according to the TSA website.

To travel with a gun, it must be unloaded in a locked hard-side case in checked baggage only.

Nationwide last year, authorities said, 4,239 firearms were discovered in carry-on bags at checkpoints across the country, averaging about 11.6 firearms per day — around a 7 percent increase from 2017.