An assistant secretary of the Department of Health and Human Services was robbed at knife point inside her home in upper Northwest Washington by a man who later tied her to a bed and escaped in her car, D.C. police reported last night.

They said that Stephanie Miller, 34, assistant secretary for public affairs, returned from a trip Friday and discovered that her home at 1704 Verbena St. NW had been burglarized. They said the two- story house in the northernmost tip of the District had been ransacked and that several items, including a mink coat, stereo equipment and cash, had been taken.

Miller reported the theft to police and changed the locks on her door, authorities said. About 6 a.m. Saturday, police said, Miller was awakened by a man standing over her bed with a knife.

The armed man then led Miller through her house for about 30 minutes in an attempt to locate valuable items, police said. He later tied Miller to a bed, police said, and told her that she would not be harmed unless she screamed or tried to escape.

The man then fled with the stolen items in Miller's late-model Datsun sports car, they said. Miller, who police said was not injured in the incident, was able to free herself from the bed and contact authorities.

Several hours later, police said, they saw a man sitting in Miller's car with the door open near the Summit Hills apartment complex in the 8500 block of 16th Street in nearby Montgomery County.

Sgt. Robert Sharkey of the D.C. robbery squad said he saw the man get out of the car, and he chased him into the apartment complex but "lost him in the maze of buildings."

D.C. and Montgomery County police searched for the man for four hours Saturday night using U.S. Park Police and D.C. police helicopters and bloodhounds, but they were unable to locate him.

Police said none of the items reported taken from Miller's home were recovered in her car. Police said they believe the man they are looking for was responsible for the first burglary at Miller's home.