The Air Force Academy (search) has begun randomly testing everyone from cadets to civilian employees for steroids (search) amid an investigation into the use of the drug among students.

The tests began last month and include active-duty military personnel at the school and students at the academy's preparatory school, along with civilian workers and about 4,000 cadets.

Four cadets, including two members of the Air Force football team, were charged with possession or distribution of steroids, the school announced last week. A fifth cadet is under investigation, academy spokesman Johnny Whitaker said.

Officials would not say whether drug tests were a factor in charging the four cadets.

The Defense Department (search) requires all military facilities to randomly test 65 percent of their populations each year for drugs, including cocaine and Ecstasy, said Betty Ann Mauger, a spokeswoman for the Air Force surgeon general's office.

The school announced the charges against running back Matthew Ward and linebacker Overton Spence Jr., along with two other cadets, on July 6. Ward and Spence were suspended from the football team during the investigation, academy spokeswoman Capt. Kim Melchor said.

The charges are the result of a campus-wide probe into drug use first announced in May.

Spence and Ward both waived their right to a hearing and the school's superintendent will decide whether either should face a court-martial. The other two, Eric M. Swartz and Jonathan S. Belkowitz, also could face a court-martial.