Searing heat may have knocked out the electricity at Chicago's Shedd Aquarium temporarily, forcing it to close for the day.
Aquarium spokeswoman Andrea Smalec says the power went out early Thursday afternoon as temperatures in the city soared above 100 degrees.
Shedd officials say it'll take time to determine if sweltering heat outside or something else was the primary cause.
Officials say emergency generators immediately kicked in and the outage never threatened any of animals
As a precaution, several hundred visitors were asked to leave and the aquarium closed for the day. It will reopen Friday.
Another spokesman, Roger Germann, says the outage occurred in parts of the building featuring thousands of fish and other aquatic animals, including turtles, lobsters and a more than 80-year-old Australian lungfish.