ESSEX, MD. -- Police were looking for leads yesterday in the bizarre execution-style slayings of two sisters and their husbands, who were found shot to death in the Baltimore County house of one of the couples this weekend.

No motive was immediately known, but a small amount of marijuana was found in a bedroom, and police said they were investigating whether the slayings were drug-related.

The television and a ceiling fan were still on when the bodies were found in the house in Bowleys Quarters, an eastern suburb of Baltimore, Baltimore County police said. Soft drinks and tea were still sitting in the family room adjacent to where the bodies were found in the living room, police said.

The victims all were found shot in the back or the back of the head, and police said there was no sign of forced entry.

"From what we can piece together right now, it appears the family may have been surprised while they were watching television in the family room sometime earlier than {Saturday}," police spokesman Brian Uppercue said. "The family was then taken into the living room where they . . . laid down on the floor, ordered to lie face down, and then were all shot."

The victims were identified as Valerie Joan Nolan, 31, and her husband, Donald Francis Nolan, 35, who lived in the house, and Laurie Ann Kroll, 26, and her husband, Kevin Kroll, age unknown, police said.

A brother of the sisters said he found the bodies of the couples about 9 p.m. Saturday lying in different parts of the living room of the house, said Uppercue.

"The motive right now would be unclear," Uppercue said, adding that the house was not ransacked.

Investigators say they believe that a gunman or gunmen got into the house while the four were watching television. No arrest had been made by last night.

The brother who found the bodies reported that the front door was locked but ajar when he arrived Saturday afternoon and that nothing appeared to have been taken.