Two enlisted men dressed in Army camouflage fatigues were arrested by Prince George's County police early yesterday after allegedly setting off two explosive devices and planting four others near an old farmhouse to be used for a Halloween horror show dubbed "Blood Manor" later this month.

Sp. 4 John G. Freeman, 22, of Harrisburg, Pa., and Pfc. Corridan Butler, 19, of Barstow, Calif., were charged with the manufacture, possession and intent to detonate explosives. Both were members of the Army ceremonial guard at Fort McNair in Southwest Washington.

The two, residents in the Oxon Hill area, told police they planted the explosives as a prank, to go off during one of the evening shows. Their "prank" could have destroyed the house and anyone in it, according to Capt. James Mundy of the county fire department.

Freeman and Butler are being held on $100,000 bond at the Prince George's County Detention Center.

They were arrested shortly after midnight when a security guard called police after he heard what he thought were two gunshots near the approximately 300-year-old structure at 3501 Steed Rd.

"I called my boss, then I called the police," said John M. Lubic, a community volunteer for the Maryland Cooperative Arts Forum, which operates the house. "The police came and we rode around the grounds, but didn't see anyone."

Lubic said one police officer, who had seen a man skulking along Steed Road, returned to the road and arrested the man, who was hiding in the bushes. The second man was arrested on the grounds of the house, Lubic said.

Both Freeman and Butler were wearing camouflage uniforms and combat boots, and had their faces blackened, Mundy said.

By the time the arrests had been made, more police cars had arrived, along with a bomb squad truck, two fire trucks, and an ambulance. Officials erected huge spotlights on a field in front of the house. Fire officials set up a campfire and prepared to stay overnight.

Investigators later searched the home of one of the two men and found seven more explosive devices assembled with homemade components.

None of the items at the home or on the grounds of the farmhouse appeared to be military equipment, Mundy said.

Although police and fire authorities would not describe the explosive devices, Lubic said one was a baby-food jar filled with black gunpowder. Another device looked like a tin can, and four others, including the two that were detonated, resembled large rifle-shell casings, Lubic said.

One of the men arrested was carrying a walkie-talkie, a small flashlight, a buck knife, a spool of wire, and an assortment of paraphernalia for rigging explosives, according to Lubic.

Freeman, who joined the Army two years ago, and Butler, in the service for a year, are both assigned to A Company of the 3rd Infantry, according to Courtney Welton, an Army public information officer. Their unit is the Commander In Chief Guard, he said, a group that performs in colonial uniforms and serves at military funerals in Arlington Cemetery.

"The unit is basically an outfit of infantry soldiers," Welton said. "They would have had very little, if any, training in the use of explosives." They were off duty Monday, he said.

Although Freeman and Butler face civilian felony charges for which, if convicted, they could get up to life in prison, Welton said the men do not appear to have violated any Army regulations. The Army will take no action pending disposition of the civilian charges, he said.

"Blood Manor" has been an annual Halloween fund-raising event held at dilapidated "haunted" houses around Prince George's County for the past 12 years. It has drawn several hundred people each year, mostly teen-agers, and is being run this year by Charles Hunter, a 25-year-old businessman.

Hunter, who said he has invested more than $10,000 of his own money to restore the 18th century home, which he rents, expects negative publicity from the arrests to complicate his efforts to produce what was to be a month-long nightly horror show.

He has already had difficulty receiving operating permits from county agencies such as the health department, he said.

Hunter, who said he helped produce "Blood Manor" shows for the county Jaycees when he was in high school, said this year he wanted to fulfill a dream of sponsoring his own production.

His plans include 15 individual staging areas in the two-story house, a crew of teen-agers to serve as ghouls and goblins, as well as sound and lighting technicians, stage managers and ticket-takers.

Hunter said he was suppose to run the show from Oct. 1 through Oct. 31, but difficulties in obtaining approval for the show from the county's Historic Preservation Commission forced him to reschedule the opening for Oct. 21.

The commission has now approved the project, he said.