Honolulu firefighters blocked off a blue, 55-gallon barrel containing an unknown type of liquid that had washed up on the beach in front of Puhuli Street and Kamehameha Highway near Sacred Falls Park just before noon today.

Honolulu fire Capt. Earle Kealoha said the barrel’s labeling and initial tests show the barrel possibly contained hydrochloric acid, a corrosive liquid used for the production of fertilizers and dye, as well as photographic, textile and rubber purposes.

It could not be immediately determined if any of the fluid leaked into the water. The container was surrounded by barnacles and firefighters at the scene said it appeared the barrel had been “floating for a while.”

The U.S. Coast Guard was notified and instructed a private contractor to remove the barrel this afternoon, Kealoha said.