The U.S. Coast Guard said early Tuesday an unknown amount of crude oil had spilled from a tank into a Louisiana waterway and the source of the leak had been secured.

The tank was being filled with crude oil when the spill occurred in Bayou Teche, a 125-mile-long waterway winding through south-central Louisiana, the Coast Guard said.

Some residents in the area were told to shelter in place as cleanup and environmental crews responded, the St. Mary Parish Sheriff’s Office said.

It was not clear how much oil had leaked into the bayou, and an investigation was under way, the Coast Guard said in a statement.

Rescue crews deployed more than 200 yards of boom to contain the oil slick and a wide stretch of Bayou Teche will be closed to all commercial vessel traffic until further notice, the statement said.

PSC Industrial Outsourcing reported the spill. The company, which specializes in metals recovery, recycling and industrial cleaning, could not immediately be reached for comment by email.