This story has been updated: More than 50 Massachusetts beaches are closed to swimming due to bacteria or algae. See a listing of beaches that are closed in Massachusetts.
Dozens of beaches along the Massachusetts coast and inland were closed to swimming over the weekend due to high levels of fecal bacteria and other water quality issues.
The state Department of Public Health listed 70 beaches online that were flagged for water safety issues as of Friday, when the DPH website was last updated — from Beverly on the North Shore down to the Cape, along with numerous inland freshwater swimming areas.
In Boston, Constitution Beach, Malibu Beach, Savin Hill Beach, and Tenean Beach were all closed to swimming after tests showed excessive levels of bacteria in the water, according to the state’s website.
The beaches remain open, but visitors will likely see signs posted warning people to stay out of the water.
“When the water quality is unsafe, the beach is required to be ‘posted’ with a sign that indicates swimming is unsafe and may cause illness,” the website says.
More than 1,100 public and semi-public beaches in the state are monitored for bacteria, according to the Department of Public Health.
Marine beaches are tested for the presence of Enterococci, and freshwater beaches are tested for E. coli or Enterococci. When bacteria levels exceed the limit for two consecutive days, the beach is posted as closed to swimmers, according to the state.
Five beaches in Beverly, four in Winthrop, three in Salem, three in Quincy, and two each in Dennis, Duxbury, Hingham, Lynn, Nahant, Revere, and Wareham were all posted on the list for “bacterial exceedance.”
High bacteria levels were also measured in nearly a dozen freshwater swimming areas that had to be closed, including Hopkinton Reservoir Upper Beach in Ashland, Silver Hill Association in Concord, and Learned Pond Beach and Waushakum Beach in Framingham.
Swimming in water with high bacteria can cause nausea, diarrhea, abdominal pain, sore throat, skin rash, eye irritation, fever, and chills, among other symptoms, according to the Department of Public Health.
Eight freshwater swimming areas in Mashpee and Miacomet Pond on Nantucket were flagged for high levels of algae and cyanobacteria, according to the website.