Neighbors thought the strong odor coming from the house on Nevada Avenue NW was a gas leak, and so they called the gas company. Not gas, said the gas company; better call the fire department. Not a fire, said the fire department; better get the police in on this.

The police knew what it was.

When officers finally entered the house early yesterday after waking a judge and getting a search warrant at around 12:45 a.m., D.C. police said yesterday, they found the source of the odd aroma that had wafted over the neighborhood: marijuana stalks burning in the fireplace.

Before the night was over, officers searching the house had confiscated about 150 pounds of high-grade marijuana valued at about half a million dollars, police said.

Police described the marijuana as a potent variety known as sinsemilla, and said discovery of such a large cache in the District was unusual.

The house, located in an affluent Chevy Chase neighborhood at 5308 Nevada Ave. NW, was unoccupied when the officers arrived, police said. No arrests have been made.

The incident began about 9:30 p.m. Tuesday when the Washington Gas Light Co. responded to investigate reports from neighbors who thought that gas was leaking from the house. When the crew arrived, they detected a strong odor coming from the house but they ascertained that it was not gas.

Another resident thought something was burning, so the gas company called the fire department, police said. Although gas company officials thought someone was inside the house, firemen responding to the call received no answer when they knocked on the door.

Police at the scene went to the back door and found it open. They went inside and found the marijuana burning in the fireplace, police said, and then subsequently found 16 boxes of the sinsemilla.

Narcotics detectives J.R. Trager and Michael Tarterra, who confiscated the marijuana, said someone had apparently been stripping the leaves from the stalks in preparation for sales and burning the the rest in the fireplace.

The detectives noted that this brand of West Coast marijuana is so powerful that the odor from the burning stalks permeated the neighborhood. Police said neighbors told them they had noticed the aroma intermittently for weeks.

The marijuana was sent to the federal Drug Enforcement Administration for further tests.