OSAN AIR BASE, South Korea — South Korean police have accused three U.S. Army officers and a government contract civilian employee of illegally shooting 90 ducks and geese near the Osan Air Base runway.

No charges have been filed against the men, a police spokesman said. The names of the accused are being withheld.

The men, apprehended by police, include a colonel and a major assigned to the U.S. Forces Korea staff and a lieutenant colonel assigned to the 6th Cavalry Brigade at Camp Humphreys, about five miles south of Osan, the spokesman said.

U.S. military and Korean authorities are investigating.

The men were apprehended shortly before 3 p.m. on Monday, less than one mile southwest of the Osan runway, police said. Hunting in the area is prohibited, and the men had expired hunting licenses, the spokesman said. When questioned, the men told Korean investigators they were shooting the birds as part of a military program aimed at keeping the Osan runway clear of birds.

Police turned the accused over to military authorities and are preparing papers to turn the case over to government prosecutors, the spokesman said.

There is confusion, however, over whether shooting the birds was illegal. The civilian involved has been a volunteer member of Osan’s Bird/Aircraft Strike Hazard program for 11 years, said a USFK official, who spoke on the condition of anonymity.

The program, operated by the base safety office, is aimed at keeping the runway clear of birds since bird strikes during landing and take off can cause aircraft to crash.

The men had paperwork signed in January 2000 by the mayor’s office in Pyongtaek, the community in which the air base is located, authorizing them to shoot birds as part of the bird strike program.

Whether that authority had expired is one of the points under investigation, USFK spokeswoman Lee Ferguson said. If the authority had expired, she said, the officers involved in the incident were not aware of it.

In the past, Osan safety officials have said that killing birds on and around the runway is done only as a last resort. Officials attempt to keep the runway clear by using other tactics, including firing a noise cannon to scare them away. Food sources and nests also are removed near the runway.

The South Korean Environment Ministry reportedly has asked USFK to punish the men.

The ministry sent a letter to USFK on Tuesday asking that personnel in the command be informed of appropriate regulations and that steps be taken to ensure such incidents do not occur in the future, Ferguson said.

Bae Gi-chul and Chon Hye-suk contributed to this report.