Officers at the Daniel K. Inouye International Airport said they discovered a firearm in the carry-on luggage of a traveler heading toward Los Angeles.

The Transportation Security Administration said a 9 mm Glock 19 handgun was discovered in a male’s luggage on Thursday at around 6 a.m. during a routine X-ray screening of carry-on luggage at the security checkpoint. TSA notified security with Allied Universal Services and questioned the traveler, who was then arrested by Hawaii State Sheriffs.

It’s the second firearm discovered by TSA in carry-on luggage at the Honolulu airport this year. The first was a Sig Sauer 320 discovered on Feb. 7. Two firearms were also discovered on carry-on luggage at the airport by this point last year.

“Firearms should never travel in carry-on luggage and be brought to the security checkpoint. The firearm discovery last week at (the Daniel K. Inouye International Airport) is reason to ask all gun owners to familiarize themselves with the procedures and rules for traveling with a firearm,” said acting Federal Security Director for Hawaii Scot Thaxton in a statement. “I continue to be grateful to the TSA officers here and across the country who work day in and day out to keep travelers safe by ensuring security threats do not make it into the cabin of an aircraft.”

The TSA may levy a civil penalty against the traveler. The recommended penalty for a firearm starts at around $2,000 and can go up to $10,000 per violation. TSA evaluates each incident on a case-by-case basis. Those with Trusted Traveler status and TSA PreCheck screening benefits will have those benefits temporarily revoked for violating firearms rules.

Firearms can be transported on a commercial aircraft only if they are unloaded, packed in a locked, hard-sided case and placed in a checked baggage, TSA said. Ammunition and firearm parts like frames, receivers, clips and magazines are also prohibited on carry-on baggage and must be checked in.

Replica firearms are also prohibited on carry-on bagged and must also be in checked luggage.

During check-in, passengers should go to the airline ticket counter to declare their firearm, ammunition and firearm parts. The TSA recommends that travelers check the gun laws of their destinations and with their airline prior to their flight to ensure that they comply with any airline-specific requirements.

More information on traveling with a firearm or other items is available on the TSA’s website.