NEW HAVEN, Conn. (WTNH) – Miles of waterfront in six Connecticut towns are all off-limits after two million gallons of raw sewage spilled into the Mill River.

The Greater New Haven Water Pollution Control Authority said the spill occurred after a 50-year-old pipe collapsed. Most of the sewage made its way to the Mill River and then flowed into the Long Island Sound, News Nation affiliate WTNH reported.

“There was a major collapse of the top of the pipe, which fell into the pipe, which then prevented any flow from getting down the pipe,” Gary Zrelak of the Greater New Haven Water Pollution Control Authority said at a news conference Wednesday.

Some people did not hear about the Monday morning spill until Wednesday morning, and in that time, some went for a swim in potentially polluted water.

Retired pediatrician Dr. Joseph Zelson often leads a group of distance swimmers in laps around Branford cove. He did just that Wednesday morning.

“As we were finishing our swim, the announcement came over someone’s phone that the beaches are closed and you shouldn’t be in the water,” Zelson said.

That warning came a little late to help Zelson and his swimmers steer clear of potentially dangerous bacteria. He expressed frustration at the slow response to the emergency.

“There are ways that they can notify people quickly. There was no sign on the beach here,” he said. “Notification should have happened much, much, much, much quicker.”

The Long Island Sound is home to more than 170 different species of fish and 1,200 different species of invertebrates, as well as sea turtles and marine mammals. Its watershed includes much of New England.