Berlin, Germany (CNN) -- The head of safety at a Namibian airport has been arrested on suspicion of placing a piece of luggage containing a "test device" among the baggage of an Air Berlin flight, the German Interior Ministry said Saturday.

The Windhoek International Airport official, who was not identified, "has confessed," the ministry said in a statement. He was arrested by Namibian police Friday evening.

Lt. Gen. Sebastian Ndeitunga, commander of the Namibian police, said the man was identified from closed-circuit television footage. Police believe the man acted alone, Ndeitunga said.

"His actions have tarnished the reputation of Namibia; it has tarnished the reputation of the Namibian security forces," Ndeitunga said at a news conference Saturday.

He declined to identify the suspect, and said any potential motives were not immediately known. He said the suspect will be formally charged Monday.

The device was found Wednesday in a suspicious piece of luggage that was about to be loaded onto the Air Berlin flight from Namibia. It was identified as a product from a U.S. company that is designed to test security.

Namibian police on Friday warned that whoever is responsible for planting the device would be severely dealt with, saying that Namibia was not to be used as an unauthorized testing ground for aviation security.

"The preliminary investigations have revealed that the suspicious parcel does not contain any explosive substances; however, it is an explosive simulation training device, manufactured by an American-based company, 'Larry Copello Incorporated,' " Ndeitunga said.

The device is a training aid to help screeners identify explosive devices, said Larry Copello, the founder and CEO of the company. Copello described the device as "non-hazardous ...not a threat to anyone."

Copello said his company sells such devices to law enforcement agencies, governments and corporate clients, but did not know to whom this particular device was sold. He learned of the Namibia incident on Thursday when the FBI called him and said he is cooperating with the investigation.

An official with the U.S. Transportation Security Administration said Friday that the agency is working with German and Namibian authorities to determine the origin of the device and the reason it was to be transported on the plane.

"We applaud the vigilance of the aviation security authorities who discovered the device and took quick action to ensure that it did not pose a threat to the aircraft and passengers," the TSA official said.

A U.S. official said Friday that there doesn't seem to be any connection with any U.S. government entity.

The discovery of the bag delayed flight 7377 to Munich, Germany, on Wednesday and raised security concerns, a spokeswoman for Air Berlin said Thursday.

The bag contained a functioning electronic clock with wiring attached, but no explosives.

CNN's Diana Magnay and Journalist John Grobler contributed to this report.