U.S. soldiers accused of firing a BB gun at pedestrians in the Itaewon bar district in Seoul and leading police on a 12-km high-speed car chase told investigators they fired the air gun for fun.

Yongsan police on Tuesday said two of the three U.S. soldiers involved in the incident agreed to undergo drug tests. Their hair and urine samples were sent to the National Forensic Service for testing.

"A test using a kit showed no traces of drugs, but we requested a more thorough test by the NFS since simple tests cannot detect traces of all drugs."

A third U.S. soldier who is in hospital with a gunshot wound is still on painkillers, but police asked American military authorities to collect his hair and urine samples for drug testing.

The two others appeared at Yongsan Police Station on Monday and admitted to firing the BB gun and speeding away in their car when a police officer approached them. But they offered conflicting accounts of who had played the leading role in the incident, according to police.