Randwick City Council said it had closed "its beloved Coogee Beach" and the Ross Jones Pool as a precaution.

Initial testing for pollution by Sydney Water came back negative, but more detailed tests for bacteria will take at least 24 hours.

"Crews responded quickly, unblocking the pipe, barricading the area, and notifying authorities as a precaution," a Sydney Water spokesman said.

"All samples taken across the beach and in the rock pool came back negative for pollution."

The blockage was caused by tree roots in pipes, which were cleared on Wednesday morning. A spokesman said the overflow was contained quickly and the area was sandbagged to capture run off.

Facebook users criticised the council for only posting the community service announcement on Wednesday evening, after it was reported the sewage overflow first occurred earlier in the day.

One woman commented that she had reported the problem at 9am on Wednesday morning, yet the Council did not close the beach until the afternoon.