Eighteen cownose stingrays and three spotted bamboo sharks have died after an apparent pump malfunction in a lagoon at a western Michigan Zoo.

The John Ball Zoo in Grand Rapids reports Friday on its website that one of two pumps for the lagoon shut down late Thursday and a backup alarm system designed to notify staff also did not function properly.

Officials say the zoo "is currently discussing the best way to honor and memorialize these amazing special animals who brought so much joy and amazement to so many people."

They say flooding from thunderstorms that began moving across the state Thursday may have shorted a circuit to the pumps.

Staff found the stingrays and sharks dead on Friday morning, and low oxygen levels were found in water samples.