South Floridians enjoying a pleasant Saturday at the beach found themselves stepping in dark, greasy balls of oil, possibly due to a spill offshore, officials said Saturday. The source of the tar remained unknown Sunday morning as the Coast Guard investigation resumed.

At 7:05 p.m. Saturday, the Coast Guard’s Southeast District posted to social media that “Coast Guard air and surface crews completed searches from Palm beach to Port Everglades for the source of the tar balls. The source remains unknown. Further assessment will continue at first light with our partner agencies.”

Fort Lauderdale Fire Rescue announced that the oily substance on the beach prompted lifeguards to tell beachgoers to stay out of the water from Riomar Street south to the Port Everglades inlet. That makes up about half of Fort Lauderdale’s beaches, said Guzman.

LAUDERDALE-BY-THE-SEA - Oily tar balls have been washing up along South Florida beaches, stretching from Fort Lauderdale to Lake Worth Beach in Palm Beach County, raising environmental concerns and frustrating beachgoers.

The U.S. Coast Guard is investigating the source of a sticky black substance washing up on some Florida beaches.

It was beautiful weather for the beach this weekend, but beachgoers found themselves in a sticky situation. The US Coast Guard reported tar balls washing up on