Police said on Tuesday they have filed for the arrest warrant of a male US national in his 70s who allegedly carried two bullets onboard a Korean Air flight on March 10.

The charges are for violating aviation security law. The suspect's current whereabouts are unknown.

Under the aviation security law, anyone who carries prohibited items onto an aircraft, or has another person do so, are subject to between two and five years in jail, or between 20 and 50 million won ($15,200 - $38,100) in fines.

The suspect flew to the Philippines capital of Manila later on the morning of March 10 on the same aircraft after passengers were evacuated upon report of the bullets' discovery, and their luggage was screened again, Incheon Airport Police told The Korea Herald on Tuesday.

"The passengers got back on board as the security screening (after they were evacuated) found no explosives, weapons or other prohibited items in their belongings," the chief of investigation at Incheon Airport Police said.

The suspect's seat had been close to where the bullets were found, the police official added.

The man had arrived in Incheon Airport from Las Vegas, and flew to Manila just three hours after police received the report that a male passenger found the bullets under his seat at 8:05 a.m. on March 10.

The flight, which had been scheduled to depart at 7:45 a.m., was returned to the terminal just before take-off. A total of 230 people aboard the plane, including 12 crew members, were evacuated.

The suspect allegedly carried two 9 mm handgun bullets onto the aircraft, airport security screening footage showed, according to the police.

Police said they will work with Interpol to arrest the suspect and find out how he brought the bullets onboard.

“We filed for the warrant yesterday, and whether it will be issued or not is expected to be decided within today,” a police official said.

Police also booked without detention a security official of a subsidiary of the Incheon International Airport Corporation, who failed to screen out the bullets before they were carried onto the plane.

Police also interrogated a Korean Air flight attendant who failed to report to police or security authorities after the bullets were found.

In a separate case of live ammunition found in a waste bin at Incheon Airport last week, police have reportedly narrowed down the suspects to 10.

Last Thursday, airport police said they received a report at 4:23 p.m. that a live bullet was found by a cleaner in the departure hall on the third floor of Passenger Terminal 1.

After analysis of footage from security cameras near the trash can, police shortlisted 10 suspects, including foreign nationals.

The 5.56 mm rifle bullet, a type used by the US military, has been sent to the National Forensic Service for examination, and the results are yet to be announced.

If the suspects have left the country, police said they will ask for Interpol’s cooperation.

The bin was located in an area accessible to non-passengers.