A mislabeled container may be to blame for the deaths of hundreds of fish at a Texas aquarium last week, officials said.

A statement posted Tuesday on the Texas State Aquarium’s Facebook page says that what staff members thought was trichlorfon, an anti-parasite drug, was actually hydroquinine, a poisonous chemical used in film processing, as a stabilizer in paint and motor fuels, and in cosmetics.

During a news conference Tuesday, aquarium CEO Tom Schmid said the hydroquinine never should have been shipped to the aquarium in the first place. He said the container was mislabeled.

“Somehow during the potentially manufacturing process, or some point in time, that container of medicine was incorrectly mislabeled,” Schmid said.

The aquarium said isn’t yet revealing the source of the mislabeled chemical.

In all, 389 fish at the aquarium were killed. Staff there are now in the process of cleaning all of the impacted tanks to remove any trace of the toxin.

Some aquariums and zoos have offered to send animals to help the Texas State Aquarium rebuild its collection.

Schmid said a fund has been established to help the aquarium recover. Orion Drilling CEO Wayne Squires has pledged to match all donations up to $50,000.

The Texas State Aquarium receives no government funding.