TRENTON, N.J. (AP) — Fifteen beaches in New Jersey that had been closed because of elevated bacteria levels have been reopened.

The state Environmental Protection Department found high levels of bacteria Wednesday and seven beaches in Atlantic City alone were closed. All of the beaches had been reopened by Thursday afternoon.

Environmental officials say heavy rains that result in runoff water containing chemicals and bird droppings is responsible for the spike in bacteria.

Atlantic County public health officer Patricia Diamond tells the Press of Atlantic City ( ) heavy rainfall on consecutive days puts a burden on the ocean. Diamond adds that bodies of water need a chance to recover.

The state will continue testing to determine when bacteria levels drop.