CHARLESTON (AP) — The Coast Guard is looking for the source of pools of thick, purple pollution in Charleston waters.

The Coast Guard said on Sunday a team was trying to determine the amount and source of the diesel-type pollutants found in three marinas late on Saturday.

Most of the pollutant had dissipated by Sunday morning and couldn’t be recovered due to heavy rainfall. Coast Guard Petty Officer 1st Class Joshua Nichols in Charleston said any remaining product should dissipate or burn off in the sunlight on Sunday.

The heaviest pockets are within Charleston City Marina. A sheen about a mile long and a quarter-mile wide is visible in the Ashley River outside the marinas.