WEATHERFORD, Okla. — Ammonia leaked from a tanker trailer in a motel parking lot in west-central Oklahoma on Wednesday, sending at least 36 residents to area hospitals and prompting evacuations in the area, authorities said.

According to Weatherford Emergency Manager Mike Karlin, authorities received a call at about 10 p.m. CT about a tanker truck possibly leaking in the parking lot of a Holiday Inn Express in Weatherford.

When authorities responded, they discovered the tanker leaking and people in the area who appeared to be suffering from respiratory distress.

Approximately 500 people were evacuated to the Pioneer Event Center at Southwestern Oklahoma State University. Thirty-six people were also hospitalized, with 11 of them transferred to Oklahoma City area hospitals for further treatment.

Karlin did not have any information about the condition of any of those victims.

Residents from three senior living facilities were also evacuated.

Police advised residents to turn off their air conditioning and/or heating systems to prevent chemicals from entering their residences.

The leak also prompted Weatherford Public Schools to cancel Thursday’s classes. Southwestern Oklahoma State University also announced it would close for the day due to the leak.

University officials said that the leak involved “anhydrous ammonia” in a statement.

Karlin said that crews were struggling with cold weather and a lack of wind.

“Unfortunately we have no wind,” Karlin said. “We haven’t had any wind all evening. We need wind to help us dissipate, we need heat to help us dissipate the product.”

Ammonia is a clear gas or liquid that occurs naturally but is also commonly used in fertilizers and pharmaceutical products, according to the U.S. Centers for Disease Control and Prevention.

“Ammonia can be recognized by its strong smell, which is like the smell of rotting fish,” the CDC said.

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