CHEYENNE -- Thirty-seven illegal aliens were arrested at F.E. Warren Air Force Base, headquarters of the nation's largest arsenal of intercontinental nuclear missiles.

Forty-four employees of a U.S. Army Corps of Engineers subcontractor were originally arrested Wednesday. Seven later provided documents showing they were in the country legally, officials said.

"Those individuals were taken into custody and they remain in our custody awaiting further investigation," INS spokeswoman Nina Pruneda said Thursday.

Twenty of the detainees were taken to the Goshen County Detention Center in Torrington on Wednesday night; 11 others were being held at the Platte County jail in Wheatland, according to Goshen County sheriff's Lt. Bryan Morehouse.

He said it isn't known how long the detainees would be held.

The aliens were working at two areas on base. Immigration and Naturalization Service officials were trying to determine whether they had access to secure areas.

However, authorities do not believe any were linked to terrorists.

Pruneda said the arrests were made in conjunction with military police and possibly other local law enforcement. She was unsure what type of work the aliens were doing.

F.E. Warren, on the west side of Cheyenne, is home to the Air Force Space Command's 90th Space Wing, which oversees 150 Minuteman III and 50 Peacekeeper missiles in silos in western Nebraska, southeast Wyoming and northeast Colorado. The Peacekeepers are being deactivated.

The base is also headquarters of the 20th Air Force, which is in charge of 150 Minuteman III missiles at Minot Air Force Base in Minot, N.D., and 200 Minuteman III missiles at Malmstrom Air Force Base in Great Falls, Mont., as well as the Warren missiles.

F.E. Warren spokesman Tech Sgt. Kenneth Smith told the Rocky Mountain News that some of the workers had bogus papers and identification cards for the construction jobs.

"I could say that a few documents were falsified," he said.

He was unsure of the aliens' nationalities.

Smith said the Army Corps of Engineers contracted the work to a construction firm, which then provided a subcontractor. The subcontractor was questioned by authorities and released.

Smith said the contracting office at Warren Air Force Base plans to look into how so many undocumented workers secured jobs at the base.