Hawaii island firefighters spent 26 hours by 4 p.m. Sunday dousing a burning propane tanker truck with more than a million gallons of water hoping to prevent a catastrophic explosion.

The incident began with a fatal collision involving an SUV and a Hawaii Gas propane truck near the 13-mile marker on Highway 19 in Honomu.

The road was closed after the crash at about 2 p.m. Saturday and remained closed Sunday while firefighters worked to keep the propane tank cool. Police said the road could remain closed today.

Police said one person died, but details on the fatality were not available.

Hawaii island fire Battalion Chief Matthias Kusch said the propane truck held about 1,750 gallons of liquid propane when it crashed. That is equivalent to 97,000 cubic feet of gas propane, or nearly enough gas to fill a 10-story building 100 feet long and 100 feet wide.

“An enormous amount of potential energy,” Kusch said. “It would be a pretty catastrophic explosion.”

While the closest homes were about 500 feet away, 70,000-volt power lines from Hamakua run through the area and authorities were concerned an explosion could cause major infrastructural damage, he said.

Firefighters were spraying water on the tank to keep it cool in the hopes of preventing an explosion from the tank rupturing with pressurized liquid still inside. The overturned truck lay off the road with a burned-out cab as firefighters waited for the gas to burn off.

Gas was escaping from a pipe that was on fire, similar to the flame on a gas stove. Firefighters wanted the flame to remain lit to prevent an explosive propane cloud from forming, Kusch said.

A 4-inch hose snaking through private yards and connected to a hydrant 2,000 feet away allowed firefighters to shoot 800 gallons of water a minute on the truck, Kusch said.

By 4 p.m. Sunday that added up to 1.25 million gallons of water on the truck, nearly enough to fill two Olympic-size swimming pools.

Kusch said firefighters coordinated with the water utility to sustain the water supply.

Firefighters did not know how much gas remained Sunday afternoon or the rate at which it was escaping, but on Sunday morning firefighters used a thermal imaging device to detect the level of liquid inside the tank and estimated 800 gallons remained at about 8 a.m. The device did not work during the heat of the day, and firefighters hoped to get another assessment overnight.