BETHESDA, Md. - A massive, aging water main ruptured yesterday and sent a wave of water down a suburban Washington road, transforming the street into a raging river and trapping nine motorists who had to be rescued from the frigid deluge by emergency workers in helicopters and boats.

The water gushed down River Road and rocked cars. Two people in a minivan were plucked by helicopter out of the roaring rapids, water crashing and spraying around them as they were lifted to safety in a basket. Other motorists escaped 4-feet-deep water by boat.

Montgomery County fire officials said that five people were checked for hypothermia; temperatures outside were in the 20s.

"The water tumbled over the car like a wave," said Silvia Saldana, of Springfield, Va., who was traveling to work when she became trapped. "I started to pray."

In a frantic 9-1-1 call released by authorities, an unidentified stranded motorist cried and pleaded for help.

"I can't see anything," the woman screamed. "I need help!"

"Stay calm, ma'am," the operator is heard saying. "We're coming."

It was not immediately clear what caused the pipe to burst. Temperature, age and other factors can contribute to water-main breaks.

Fire spokesman Pete Piringer said that crews had trouble getting to people because of the swift-moving water. Officials said that 150,000 gallons of water per minute were rushing out at one point, spilling rocks, dirt and other debris onto the road.

Trees fell onto a power line and knocked down a utility pole. Schools in the county closed early because of widespread water outages. A hospital where three people rescued were treated and released diverted ambulances and closed its trauma division because of lost water pressure.

Hebert De Rienzo tried to turn his small hatchback around as water began rising in and around his car, splashing on him and his fiancee. Christmas presents were ruined.

"We couldn't open the windows because the water would come through," he said. "We were scared." *