Thousands of gallons of untreated sewage poured into a creek in upper Montgomery County on Wednesday as utility crews searched for a break in a 16-inch sewer pipe, authorities said.

It marked the second day in a row sewage was leaking through the ground and spilling out of manholes near a sewage pumping station in Brookeville at a rate of 100 to 500 gallons a minute, said I.J. Hudson, a spokesman for the Washington Suburban Sanitary Commission.

The break was first discovered about 11:30 a.m. Tuesday. The sewage bubbled up into the creek from underground and flowed into the waterway from the manholes about 25 feet away, he said.

“It’s safe to say it will be in the hundreds of thousands [of gallons] by the time this is over,” Hudson said. “We certainly do what we can to keep this from happening.”

Crews found the pipe about 15 feet underground but had not located the break as of Wednesday evening, Hudson said. He said the WSSC doesn’t know what caused the break near the pumping station, at 2611 Brighton Dam Rd.

Reddy Branch Creek, where the spill occurred, eventually feeds into the Patuxent River upstream from the Rocky Gorge Reservoir, which contains much of the WSSC’s drinking-water supply.

WSSC spokesman Jim Neustadt said the utility is “watching it closely” but that the sewage will be diluted in the 4.5-billion-gallon reservoir long before it reaches the water-treatment plant. The pathogens can’t survive the reservoir’s low temperature, he said.

Drinking water also is tested for contaminants throughout the treatment process.

“The drinking water is fine,” Neustadt said, adding, “We will take additional precautions as necessary.”

The utility, which provides water and sewer service to 1.8 million residents in Montgomery and Prince George’s counties, is under a court order to reduce the number of sewage spills. The order stemmed from a 2005 legal settlement with the U.S. Environmental Protection Agency, the Maryland Department of the Environment and four environmental groups that sued the utility, accusing it of violating the Clean Water Act by having too many sewage overflows.

Under that consent decree, fines can be assessed for spills, said Jay Apperson, a spokesman for the Maryland Department of the Environment. The WSSC has five days to submit a detailed report to the state.

Don Chamberlin, spokesman for the Patuxent Watershed Protective Association, said he’s concerned about the spill’s impacts.

“We’re not just talking about ‘You can’t go play in the water,’ ” Chamberlin said. “This is people’s drinking water.”

He said this spill is far worse than other sewer pipe breaks because most sewer pipes aren’t pressurized. Flowing at a rate of up to 500 gallons a minute, he said, means that “the sewage could be measured in dump-truck loads. It’s a big spill.”

Because the pipe was pressurized, WSSC crews turned off the pumping station to reduce the amount of sewage escaping it. But that caused sewage to flow out the manholes, Hudson said.

As people in the Olney and Brookeville areas continued to flush toilets and take showers, he said, sewage continued to flow into the pumping station and out the manholes. The sewer system doesn't have additional pipes to allow WSSC officials to divert the sewage around the break, as they often can with a water main break, Hudson said.

Sewage will continue to flow out of the manholes until the pumping station can be turned back on, he said. But that can’t happen until the source of the break is found and that section of pipe is replaced.