WEATHERFORD, Okla. — Hundreds of people were evacuated from a city in Oklahoma and others were told to shelter in place after a tanker truck that was leaking in a hotel parking lot spewed a plume of anhydrous ammonia gas, authorities said Thursday.

The gas release happened shortly before 10 p.m. Wednesday. People in the immediate area were in respiratory distress and at least 36 people were taken to a local hospital, city officials said at a news conference. Eleven of them were brought to other hospitals for further treatment.

At least 500 to 600 people were in a shelter as of Thursday morning, authorities said. Several nursing homes were evacuated and schools were closed for the day. Those that were told to shelter in place were in a triangle-shaped area, including businesses that were advised to stay closed, authorities said.

Krystal Blackwell, who was evacuated, said emergency officials were wearing gas masks and knocking on doors.

“It was a little crazy to wake up to,” Blackwell told KWTV-TV. “I really thought it was a kind of dream.” She said she was sitting in her car, still wearing her pajamas.

Authorities said the air quality was being monitored and that the tanker truck was no longer spewing gas, but that a lack of wind was slowing efforts to dissipate it. A number of agencies were on hand to assist, including hazmat crews and an Oklahoma National Guard unit that supports first responders during emergencies.

An exit from Interstate 40 to Weatherford was shut down, authorities said.

Anhydrous ammonia is used as a fertilizer to help provide nitrogen for corn and wheat plants. If a person touches it when it is in gas or liquid form, they could be burned. Last week, an anhydrous ammonia leak caused by an explosion at a plant north of Yazoo City, Mississippi, prompted evacuations for nearby residents.

Weatherford has about 12,000 residents and is about 70 miles (113 kilometers) west of Oklahoma City.