A Forestville couple has been arrested in the slayings last week of a Montgomery County police officer and a security man during the burglary of a catalogue store in White Oak.Police said they are still seeking at least two other suspects.

According to one law enforcement source, investigators are exploring the possibility that burglars may have opened fire inside the W. Bell & Co. store on New Hampshire Avenue because they were recognized by the guard, the policeman or a store manager, who was wounded but survived the confrontation.

Under this theory -- called speculation by the official Montgomery County police spokesman -- one of the burgulars had a relative who was once employed by the store and who provided insider's assistance in the break-in early Friday.

Burl Perry Courtney, 22, operator of a snack vending truck, and his 21-year-old common-law wife, Valerie Lawson, were arrested at their home about 6 a.m. Tuesday as a result of an informant's tip. Montgomery County police said they withheld disclosure of the arrests until yesterday to allow time for questioning the couple and to develop leads that might result in apprehension of the other suspects.

Courtney and Lawson were asleep when special weapons teams and detectives went to their home at 6202 Surrey Square La., according to police. Their year-old child was reported to have been placed with a relative when police took them away.

Courtney was charged with two counts of murder and one each of attempted murder, armed robbery, burglary and use of a hand-gun. Lawson was charged with being an accessory after the fact to murder.

Lawson is accused of knowing of the burglary plans in advance, providing a car used in the crime and harboring Courtney afterwards.

Police would not identify any additional suspects, but applications for the warrants for Courtney's and Lawson's arrests say that one is a convict who was serving 50 years for murder before escaping from an unnamed prison two months ago and that a second suspect has been identified by an informant, according to United Press International.

Police would not discuss their continuing investigation yesterday. At least 10 officers have been assigned full time to the case.

The shootings occurred as Montgomery County police officer Philip Metz, 33, and David Wayne Myers, 30, a security technician of a burglar alarm company, checked the W. Bell building after at least two burgular alarms were activated shortly after 7 a.m.

Police said the bodies of Metz and Myers were found in an office where the store's safe was located. A store manager, Douglas Cummins Jr., 28, was shot, then handcuffed to a file cabinet and apparently left to die. Cummins survived and later called police.

Police said yesterday the information that led to Tuesday's arrests was received in a telephone tip on Monday. They did not name the informant. The arrests, in Prince George's County, were made with the assistance of Prince George's police.

Metz was the first Montgomery police officer killed in the line of duty since 1976. Hundreds of police officers from 42 different departments attended his funeral on Monday.

The shootings at the catalogue store were followed 14 hours later by the fatal shooting in Hillandale of the manager of a Grand Union supermarket, also on New Hampshire Avenue less than two miles away. No arrests have been made in that shooting, which occurred during a holdup. Police said it was apparently unrelated to the White Oak incident.

Courtney and Lawson were held yesterday in the Montgomery County Detention Center in Rockville, Courtney without bond and Lawson under $25,000 bond.

At a bond hearing in County District Court, a judge cited the severity of Courtney's alleged offense and current unemployment as factors in denying bond. Courtney's court-appointed attorney said he is not unemployed, but his work -- selling ice cream, sodas, candy and assorted snacks on the streets of Washington -- is slack during the winter months.

The owner of an ice cream and snacks wholesaling firm where Courtney used to stock his vending truck remembered him yesterday as energetic, quick to make a joke, "the kind of kid you'd like to take home to introduce to your parents." aHe said Lawson often rode with him in the truck when he stopped by to pick up supplies.