Heavy rains overnight caused two separate sewer main breaks in Haverhill, Massachusetts, that are causing sewage to flow into the Merrimack River.

The mayor’s office said in a Facebook post that around 9 p.m. Friday during torrential rains, the city experienced a break in a 42-inch sewer main near its main pumping station. The heavy rainfall caused wastewater flows to increase rapidly, placing “significantly greater demand” on the pipeline.

The Department of Public Works has been working continuously since Friday night, the mayor’s office said. As they were investigating the damage on Saturday, they discovered a second sewer main break, which requires additional assessment to determine the needed repairs.

They said the discovery of the second break means the damaged area is larger than originally believed.

“The City’s priorities are to protect public health, stop the discharge into the Merrimack River as quickly as possible, maintain sewer service to the community, and complete a safe and permanent repair,” the mayor’s office added.

Because of the two breaks, untreated wastewater is being discharged into the Merrimack River downstream of Haverhill’s downtown area instead of reaching the city’s wastewater treatment plant. The city’s sewer system remains fully operational, with no interruption anticipated. The city’s drinking water system is separate from the sewer system and is also unaffected.

The city said it has notified the Massachusetts Department of Environmental Protection, the U.S. Environmental Protection Agency and other required regulatory agencies.

The public is being advised to avoid contact with the Merrimack River in the immediate area and downstream of the discharge until repairs have been completed.

“The City’s immediate objective is to stop the discharge into the Merrimack River while maintaining sewer service throughout the community,” the mayor’s office said. “Because this is one of the City’s largest and most critical wastewater pipelines, the repair must be completed carefully and correctly. Simply shutting down the pumping station is not an option because it serves thousands of homes and businesses. Doing so would potentially cause wastewater to back up into the collection system, potentially resulting in sewer backups and additional overflows elsewhere in the City.”

The exact cause of the failures remains under investigation.