The body of a 40-year-old Bowie man who had been missing since Wednesday night was found yesterday near a vacant house not far from Dulles International Airport, according to the Loudoun County sheriff's office.

Police say they have not determined how John Frank Cirios of 8400 Spruill Dr. died, but suspect foul play.

Officials have made no arrests, and declined to release further details, pending an autopsy scheduled for today by the Northern Virginia medical examiner's office.

Cirios' body was discovered at 6:30 a.m. yesterday by a passing hunter, police said. It was found near Ashburn in the bushes off Virginia Rte. 642 (Hay Road), about one-half mile east of Rte. 659 (Belmont Road), according to Sgt. Terry McCracken.

If Cirios was slain, McCracken said, he would be the fifth homicide victim so far this year in a county that usually records only two or three a year. "This is very high for us," he said, adding that the deaths do not seem to be related.

Although the site where Cirios' body was found is only half a mile from the Washington & Old Dominion bike trail where missing jogger Judith DeMaria was last seen in August, police said there is no apparent connection to that case, either.

Cirios, described by police and neighbors as very punctual and dependable, was last seen at 5 p.m. Wednesday at the Alban Tractor Co. on Sully Road in Sterling, where he worked as a corporate trouble-shooter and liaison between the manufacturer and Alban.

That evening, he failed to pick up his 9-year-old daughter from a baby sitter in Bowie. Police said Cirios had custody of the child and that he and his wife had not lived together for some time.

On Thursday morning, Cirios failed to report to work, and colleagues noticed that his maroon pickup truck was still in the parking lot, police said. He had worked for Alban since 1969.

Cirios' body, found about three miles away from the tractor company plant, was identified yesterday by a co-worker, police said.

An intensive two-day search of the woods near the plant was called off Saturday afternoon after police, volunteers, dogs and a Fairfax County helicopter failed to detect any traces of the missing man.

Friends said Sunday that the baby sitter has continued to care for Cirios' daughter since his disappearance.

If the child seems to have no guardian or relatives able to care for her, the county will study the case, said Bernadette Shomers, a spokesman for the Prince George's Department of Social Services.