The U.S. Coast Guard has been searching for tar balls that began showing up on Florida beaches over the weekend. So far, the source of the black muck remains a mystery.

After aerial flights and physical searches, the Coast Guard says the little blobs of oil are no longer floating ashore.

Over the weekend, something unusual washed up along South Florida beaches. The United States Coast Guard spent this past weekend investigating reports of tar balls from Lake Worth Beach to Boynton Beach and as far south as Fort Lauderdale Beach.

What's the source of the dark goop washing up on Florida's beaches? The U.S. Coast Guard is scanning the shores from Port Everglades to Palm Beach after locals reported sticky balls of sludge amid the sands.