Five wastewater treatment plants dumped sewage and storm water into the Merrimack River on Wednesday night, right in the midst of a four-day kayaking trip involving local officials and politicians.

The Merrimack River Watershed Council said the amount of sewage released into the river was not known as of Thursday, but appeared to be significant due to the number of plants that released.

The council said health officials have advised that people do not have direct contact with water for 48 hours after a CSO discharge. The trip, however, is continuing on, said state Sen. Diana DiZoglio, D-Methuen.

The council said the Lowell wastewater plant reported a five-hour long release, which started at 9:56 p.m. Wednesday and ended at 3:11 a.m. Thursday. The city also had an hour-long release earlier in the day Wednesday.

Haverhill reported releases from nine of its 15 overflow pipes, according to the council. The storm dropped 2-1/4 inches of rainfall in the city.

Cheri Cousens, executive director of the sewage district, said the Greater Lawrence Sanitary District reported outfall from three out of its five pipes. Cousens said the longest duration of outfall was over three hours, and the other two lasted half an hour or less.

About 1.64 inches of rainfall was reported in Lawrence, said Cousens.

The Nashua, New Hampshire, sewage treatment plants reported "probable" releases from three of its nine outflow pipes.

The council said Manchester's sewage treatment plant, which is the largest CSO pollutant to the Merrimack, does not alert the public when it releases sewage into the river. The New Hampshire Department of Environmental Services, however, confirmed Manchester released sewage during the storm.

While the sewage and storm water didn't put an end to the four-day kayaking trip down the river, which kicked off Wednesday, DiZoglio said she was concerned about the situation.

"Knowing that there have been sewage discharges is definitely concerning," she said. "We are continuing on and taking the trip in stride, because one of the big reasons we are doing this 117-mile trip is to raise awareness around the importance of the river's overall health, and the continued need for attention from our elected officials, community activists and residents."

The trip, taken by officials like DiZoglio; Rep. Christina Minicucci, D-North Andover; and Lane Glenn, Northern Essex Community College president, among others, is aimed at drawing attention to environmental conservation and recreational access to the Merrimack. Their journey began at the start of the river in New Hampshire and will end at Plum Island.

In 2018, the five sewage systems along the Merrimack River reported hundreds of discharges amounting to more than 800 million gallons of untreated sewage and storm water.

The discharges typically come during heavy rainfall — like the storm Wednesday night — when dozens of overflow pipes that belong to the aged sewer and storm water systems designed to spill are overpowered.

In New Hampshire, the Manchester treatment plant alone released an estimated 227 gallons of sewage through 15 outfalls, according to the State Department of Environmental Services.

About 500,000 people get their drinking water from the Merrimack River.

DiZoglio co-sponsored a bill passed in the senate last week to formally create the Merrimack River District Commission. The group would review the health of the river and work to improve and restore water quality, she said.

"We need to bring environmental experts, engineers and stakeholders from throughout the region together to collaborate and find realistic solutions regarding updating old infrastructure and keeping the river clean," DiZoglio wrote during her trip Thursday.