Lutz, Fla. ? The bodies of two college students were found Saturday inside a large, deflated helium balloon at the entrance of a condominium complex a few miles north of Tampa.

The 8-foot-diameter balloon was used to advertise the complex.

The deaths of Jason Ackerman and Sara Rydman, both 21, appear to be accidental, Hillsborough County Sheriff’s Maj. Bob Schrader said.

“It was more a fun thing they thought they were doing,” said Linda Rydman, whose daughter was found dead. “You know how you blow up the balloon and suck the helium.”

Inhaling helium can quickly lead to brain damage and death from lack of oxygen, according to the Compressed Gas Assn., which develops safety standards in the gas industry.