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. Officials say tests found the balls to be formed from chemicals similar to those in cosmetics and cleaning products but it is still unclear where they came from. Eight beaches including Bondi – the city’s most famous – were closed and a massive clean-up ordered amid fears the black deposits were toxic. New South Wales’s Environment Minister, Penny Sharpe, said investigations were continuing to establish the source of the pollution and who was responsible.