When she opened the garage door of her brother-in-law's Silver Spring home Wednesday afternoon, Marie Loutoo thought she detected the faint smell of car exhaust.

"I thought someone had just come home and pulled into the garage," Loutoo, 41, said yesterday. "But it seemed strange. I couldn't understand why both cars were in the garage in the middle of the day."

Loutoo discovered why minutes later, in a macabre walk through the split-level house, where she discovered the bodies of five family members who police said died of carbon monoxide poisoning after a car in the garage was left running overnight in the closed garage and filled the house with deadly fumes.

Montgomery County police investigators said yesterday that they believe the deaths of Prakash "Ray" Raman, his wife, two children and a cousin were an accident, not a deliberate act. They added, however, that the investigation would not formally be complete for weeks.

"We found no suicide notes, and there did not appear to be any discord among family members," an investigator said. "It looks right now like someone simply forgot to turn off the car, and it became a tragedy."

Montgomery police spokeswoman Ann Evans said that blood tests performed yesterday confirmed that all five family members died of carbon monoxide poisoning. The victims, besides Ray Raman, 51, were identified as his wife, Esther, 48; son, Rishi David, 20; daughter Rehanna, 19; and a cousin, 57-year-old Lalchan "Lally" Jagroo. The only survivor in the immediate family returned home yesterday. She is a daughter, Ria Raman, 27, of New York.

Loutoo discovered the five poisoning victims about 12:45 p.m. Wednesday as she and Esther's mother, Margaret Loutoo, were paying the Ramans a visit. Loutoo said that when no one came to the front door, they entered the house through the garage, which is connected to the kitchen and is located beneath one of the home's bedrooms.

She said she punched in the electronic combination to the garage door opener and detected faint fumes as soon as the door began to swing up. "It wasn't a strong odor," she said. "I thought it might even be from the traffic on the street."

The women discovered that the door leading to the kitchen was closed but not locked. They walked inside, and as the elderly Margaret Loutoo sat in a chair to rest, Marie walked upstairs.

She first found Rehanna, lying in bed with her back to the door. Rehanna had recently been found to have Hodgkin's disease, and Loutoo said she assumed the teenager was not feeling well and was sleeping late.

"Something told me to shake her," Loutoo said. "But when I touched her, she was cold and stiff. I didn't know if she was dead, but I knew she was in trouble.

"I called out for Esther or someone to come help me wake her up. But the whole house was quiet."

Loutoo said she then ran into the parents' room, where she found Esther sitting upright against the headboard of the bed, her eyes closed. She, too, was pale and motionless.

"There was a white foam around her mouth," Loutoo said, her voice beginning to break into sobs. "I started to get scared. I turned around to run out." She then saw Ray Raman crumpled on the bathroom floor, a razor in his hand. Loutoo rushed to a phone and called 911. Several minutes later she discovered Rishi's body on the floor of his downstairs bedroom and Jagroo dead in a downstairs bathroom. "All of those bodies, I couldn't believe what was happening," Loutoo said. "It was like a horrible dream. They were such a wonderful family."

Relatives have told police that Ray Raman and Jagroo had returned Monday from a Memorial Day weekend visit to family in Delaware. The two had their belongings in the trunk of their Nissan Altima, and an investigator said the men may have pulled into the garage left the car running as they popped the electronic trunk release and begun carrying items into the house.

"They may have gotten sidetracked putting things away and forgotten the car was running," the investigator said. "If it were a suicide, or deliberate, the kitchen door probably would have been left open to let the gas in. But it looks like the fumes slowly seeped into the house through the night." Carbon monoxide is a colorless, odorless, highly poisonous gas given off by a car's exhaust system , gas ovens, barbecue grills and unvented space heaters.

Police said that when they found the car, the ignition was on, the battery was dead and the fuel tank was empty. Loutoo said that funeral arrangements have not yet been made.

"Right now we're just trying to get all the remaining family together and get through this," she said. "We're still in shock." CAPTION: From left, Ray Raman, 51, Rehanna Raman, 19, Rishi David, 20, and Esther Raman, 48, were all found dead in their bedrooms in the family home.