The electric power cable leak that spilled oil into Mill River in East Rockaway has been stopped and repairs have begun, a spokeswoman for PSEG Long Island said Thursday.

“Crews have located the leak on the southwest corner of Atlantic Avenue and Access Road and are working around the clock to make repairs to the affected cable,” PSEG Long Island spokeswoman Elizabeth Flagler said in an email. “The flow of the nonhazardous dielectric fluid has ceased.”

The leak, estimated at about 1,000 gallons by the Nassau County Fire Marshal's office, was discovered Monday. It triggered a cleanup response that continued Thursday, as boat crews hauled in absorbent material that was laid out in ribbons on the water’s surface around the Edward A. Talfor Memorial Boat Basin.

PSEG contractors were working Thursday on "exposing the cable to evaluate the damage and plan for repair," according to a statement from the state Department of Environmental Conservation.

On Wednesday, a crew had begun tearing up the road at Atlantic Avenue by Access Road, closing a lane and snarling eastbound traffic. On Thursday, traffic headaches persisted along Atlantic Avenue as excavation work continued.

Three workmen stood inside one large hole, below grade, digging with hand shovels after a vacuum truck had sucked out a brown fluid that quickly refilled.

“Once the damage is determined, repairing an underground cable can take several weeks,” Flagler said.

The DEC said in its statement that "it is continuing to closely oversee the investigation and cleanup."

Dielectric oil is a mineral oil, nontoxic to humans, used to cool high-voltage power lines. Flagler said the system is monitored, and when the oil pressure drops, it triggers an alarm.

Two environmentalists expressed worries Thursday about potential harm to the environment and wildlife.

“The thing with this dielectric fluid is that even though it's nontoxic to humans, it doesn't biodegrade naturally,” said Adrienne Esposito, executive director of Citizens Campaign for the Environment, a statewide environmental advocacy organization with an office in Farmingdale.

Esposito said the spill could harm fish and birds in the area.

“The biggest concern is that it is damaging to birds because it gets in their feathers and causes them to be smothered and unable to fly, and then they can either starve or die,” Esposito said.

Robert Weltner, president of Freeport-based Operation S.P.L.A.S.H., a nonprofit that organizes cleanups of South Shore waterways and waterfronts, said he worked with dielectric oil in his past career as an electrician.

While it’s not toxic to humans, “They wouldn't let you swim in it; it's nasty stuff,” Weltner said. “But to the wildlife out there, it's devastating … fish and birds, they don't have a choice. They are swimming in it.”