INDIANAPOLIS -- Several sharks at the Indianapolis Zoo died early Tuesday after too much of a chemical was added to their tank.

Zoo spokeswoman Judy Gagen said 15 bonnethead sharks held in the Oceans building were found dead Tuesday.

Veterinarians at the zoo said that the sharks died as a result of too much ozone, which they described as an oxygen molecule in an electrically charged state that oxidizes, or dissolves, organic waste products in a pond or fish tank.

A system in the sharks' tank was taken offline for maintenance Monday night and was therefore unable to provide an accurate signal to the ozone generator, which continued to add ozone to the water overnight, Gagen said.

Two emperor snappers also housed in the tank survived the incident.

Gagen said zoo staff would be reviewing the tank system design and procedures regarding repairs.

The average bonnethead shark, also known as the shovelhead shark, is a small, common hammerhead shark with a smooth, rounded head. They average about 3.3 feet and are usually found in the western Atlantic and eastern Pacific Oceans.

Gagen said the sharks will likely be replaced.