TAMPA (WFLA) — Officials at a zoo in Tampa, Florida are investigating after 12 stingrays died this week.

ZooTampa at Lowry Park announced the deaths on Facebook Thursday night.

“It’s with heavy hearts we share that today ZooTampa lost 12 residents of Stingray Bay,” the post said.

According to the post, the zoo’s animal care and veterinary teams are examining all of the mechanical equipment involved to figure out what happened. They’re also testing the water in Stingray Bay. So far, the zoo says all evidence indicates “optimal water quality and conditions.”

Zoo officials say it may take several weeks for all of the test results to come in. They also noted that Stingray Bay is a closed system that only houses rays.

“Please keep our team in your thoughts – every professional here loves the animals we care for, and any loss is a difficult one,” the Facebook post said. “Thank you for your support.”

The post drew hundreds of comments with many people posting photos of family visits to see the sting rays.

“Heartbreaking, this is the one place we have to visit every time,” one person wrote. “These rays were so sweet. Thinking of the staff that have cared for them along the way and hope they find some answers.”

“I am so sorry,” wrote a mother who shared a photo of her son petting one of the rays. “We have plans to go there Sunday and this is my son’s favorite place to visit. He especially loved Brownie. He will be heartbroken, as I’m sure all of the care team is as well.”

Stingray Bay will remain closed for now.