Beaches in Sydney reopened after being closed earlier this week when hundreds of mysterious golf ball-sized black lumps washed ashore. These dark spheres, which were first spotted on Coogee Beach on Tuesday, were confirmed to be “tar balls” but it was unclear where they originated from.

Beaches in the Australian city of Sydney have reopened for swimmers after being closed earlier this week when thousands of mysterious black tar-like balls washed ashore, prompting health concerns.

Sydney’s Bondi Beach and other beaches around the Australian city were shut on Thursday as officials investigated mysterious tar balls that have washed ashore.