Vessels were being urged to travel carefully through the Mobile shipping channel on Tuesday after two boats containing 2,000 gallons of oil capsized the previous night, leaving a mile-long sheen, the U.S. Coast Guard Mobile Sector said. Five crew members were rescued from the 52-foot (15-metre) Delta Amber tugboat and the 26-foot (8-metre) Nicholas as the two ships sank around 10:45 p.m. The cause of the capsizing of the two boats, which were both employed in a dredging operation in the bay by Mike Hooks Inc, is under investigation by the Coast Guard. A boom was placed around the sunken boats to prevent the fuel and lubricating oil inside them from disseminating into the bay. However, Lieutenant Bradley Parker said that “some oil has escaped and is emitting a sheen in the bay.” Vessel traffic through the shipping channel has been uninterrupted, but Petty Officer Chad Jackson with the Coast Guard Mobile Sector said they are “urging folks to transit the area with caution.” A salvage operation is being led by Oil Recovery Corp. at the site of the capsizings, which occurred north of Gaillard Island at the edge of the shipping channel.