The boil-water advisory in effect since Monday for a large part of Prince George's County was lifted Thursday morning after a second test showed that water is safe to drink following a water main break, said officials from the Washington Suburban Sanitary Commission.

However, as a precaution, customers were told to run taps on cold water for five minutes before drinking the water. WSSC officials suggested starting with the highest faucet in a home or business and then opening other faucets, moving from the highest floor to the lowest. After five minutes, faucets should be turned off in reverse order, from lowest to highest.

Water dispensers on refrigerators also should run for five minutes.

Any ice made after 1:30 p.m. Monday should be thrown away, along with the next three batches of ice produced after the advisory was lifted at 8:45 a.m. Thursday, WSSC officials said. Ice-maker containers should be wiped clean with a solution of two tablespoons bleach to one gallon of water.

WSSC spokesman John C. White said the utility is recommending the extra precautions to ensure that no one drinks water that possibly could have been contaminated before the first clean test samples were taken Tuesday.

"You can never be too safe," White said.

The boil-water advisory affected about 400,000 people south of Central Avenue and Landover Road after a major pipe break in Capitol Heights on Monday morning. The advisory was a precaution, WSSC officials said, because contaminants can seep into the system more easily when a pipe break causes a pressure loss.

The break about 3:50 a.m. flooded nearby businesses and vehicles, closed part of the Capital Beltway for several hours and left a sizeable swath of Prince George's without water for much of the day.

Water samples taken Tuesday and Wednesday showed no contamination, WSSC officials said.

Crews that stopped work Wednesday during the snowstorm resumed work Thursday morning to remove two sections of the broken 54-inch pipe, WSSC officials said. The pace of the pipe repairs does not affect customers, because water has been diverted through another main, they said.