Ollin R. Crawford, 26, the Laurel woman charged in one of a series of six "Hand Grenade Lady" bank robberies, was for three years an officer with the Army Military Police at Fort Belvoir and would have had access to grenades while she was there, Fairfax County police said yesterday.

But police said no grenade was found during a search of Crawford's apartment, which she permitted when she was arrested Wednesday afternoon by Prince George's County police.

Crawford is four months pregnant and has told police that she is innocent, they said.

Police say Crawford is a suspect in all six incidents in which a woman entered area banks, displayed a brown sock containing a lemon-shaped object, claimed it was a grenade, and demanded money. Fairfax County prosecutor Robert F. Horan Jr. said yesterday that the five successful robberies netted more than $10,000 -- "but not a lot more."

Crawford waived extradition to Virginia and was taken late yesterday afternoon from Prince George's County to Fairfax County, police said.

She is scheduled to be arraigned this morning in Fairfax County General District Court on a charge of robbing the First American Bank at 6565 Little River Turnpike on Aug. 27. That robbery was the second in what police say is a series of similar robberies.

Crawford was an M.P. at Fort Belvoir from 1980 until June 1983, according to Fairfax police spokeswoman Connie Curran. Police said they do not know yet why she left that position.

Crawford's arrest capped an eight-week investigation by Fairfax police that officials said yesterday was one of the most intensive in a decade.

Last Thursday, the "Hand Grenade Lady" walked out of a Baileys Crossroads bank empty-handed when the drawer from which she demanded money turned out to be empty.

The next day, Fairfax County police staked out 44 banks in the Annandale and Baileys Crossroads areas for more than six hours, Curran said.

Police said the robberies had by that time fallen into a pattern: the first two came two days apart at the end of August; the next two came four days apart at the end of September.

After Thursday's unsuccessful attempt at the end of October, Curran said, police thought she would strike again quickly.

But she stood up the largest stakeout in the department's recent history. Police did arrest a Richmond man who robbed one of the staked-out banks.

On Monday, the "Hand Grenade Lady" struck again, robbing a First American bank in Springfield that had not been staked out.

The six robberies were so similar in technique that police believe they were all committed by the same person. Five of the robberies occurred in the Springfield and Annandale areas of Fairfax County and the sixth took place in Wheaton.

A slim woman, wearing a baggy gray sweater, sunglasses and a gray beret entered each bank, gave a teller a note declaring she had a grenade and demanding money. Police say they have no way of knowing whether the woman actually had a grenade.

Curran said some clothing similar to that worn by the "Hand Grenade Lady" was taken from Crawford's home.

The string of robberies consistently frustrated police, who said they considered Crawford a suspect immediately after the second robbery, after being tipped off by a call to the county's Crime Solvers program.

And in none of the cases in which she received cash did she get a red dye package, which explodes shortly after a robbery, making robbers easier to catch.

A warrant for Crawford's arrest was obtained Oct. 15, but police did not then know Crawford's address, 200 Fort Meade Rd., until more Crime Solvers tips came in this week.