A decision by Prince George's County fire officials last week to allow a fire from an overturned propane tanker to burn itself out rather than trying to put it out was the "only acceptable and viable" response to the accident, county fire investigators said yesterday.

The fire and threat of an explosion closed a portion of the Capital Beltway for 16 hours last Friday and Saturday, leading to a massive traffic backup, and caused the overnight evacuations of several hundred area residents.

Fire officials said yesterday that an investigation of the incident showed that seepage of the highly flammable gas from the tanker could not have been stopped and that any attempt to put out the fire could have led to a violent explosion.

The truck, loaded with 1,600 gallons of propane, turned over and caught fire on I-495 south of Laurel shortly before 1 p.m. last Friday.

The fire burned out more than 13 hours later.

Fire department spokesman Tony DeStefano said that investigators who examined the truck this week found that pipes connected to the tank had been cracked in the accident, permitting the gas to seep out.

Seals on tank valves were melted away, he said, making it impossible to turn off the flow of gas.

Officials are still investigating the cause of the accident.