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.

Beaches in Sydney including the iconic Bondi were closed to bathers on Thursday after hundreds of black balls suspected to be toxic washed up on the city's shores.

Penny Sharp, the environment minister of New South Wales, said investigations were continuing to find what was behind the formation of these tar balls. Waverley Council closed Bondi, Bronte, and Tamarama beaches as a precaution on Thursday evening,

Sydney beaches reopened on Saturday after thousands of tar balls had been washed ashore earlier this week. Since Tuesday, little balls made up of oil, debris, and other pollutants have littered popular eastern suburbs,