Coast Guard spokeswoman Natalie Murphy said the tar mat was about 165 feet long by 65 feet wide, and weighed more than 40,000 pounds, mostly because of sand, shells and water, CNN reported Tuesday.
The mat was found beneath the surf off Isle Grand Terre, 90 miles south of New Orleans. Crews used an excavator to remove the largely submerged tar mat from the beach in chunks during the past few weeks, Murphy said.
Louisiana is the only state still conducting regular cleanup operations from the oil spill. The Coast Guard and BP, owner of the ruptured well, declared the cleanup finished in Alabama, Florida and Mississippi earlier this month, CNN said.
More than 80 miles of the Louisiana coast are still being patrolled. So far this year, BP recovered more than 2.7 million pounds of waste from Louisiana shores, with residual oil making up between 5 percent and 15 percent of the total weight, company spokesman Jason Ryan told CNN.
The Deepwater Horizon rig exploded and sank in April 2010, killing 11 men aboard and unleashing an undersea gusher in the Gulf of Mexico.