A Chicago man was arrested at Oakland International Airport Friday after security employees found a knife in his carry-on luggage, according to the Transportation Security Administration.

The 38-year-old man was on his way to Las Vegas via Spirit Airlines flight 915 when the butterfly knife with a 4-inch blade was found, TSA spokesman Nico Melendez said.

The man told TSA officials he had "forgotten the item was in his bag," and "was unaware the item was prohibited," Melendez said. In addition to the arrest, he faces civil penalties of up to $11,000.

Passengers are prohibited from carrying sharp objects in carry-on luggage, but can place them in checked bags.

TSA officials also made arrests in Long Beach, Calif. on Thursday and in Ontario, Calif. on Wednesday in connection with the discovery of loaded guns.