Plane makes emergency landing in San Antonio

SAN ANTONIO (Reuters) - A Continental Airlines Boeing 737 jet that had just taken off from San Antonio International Airport was forced to make an emergency landing back at the airport on Thursday morning due to a strong odor of chemicals on the plane.

"There was a report of a strong chemical odor in the cabin," San Antonio airport spokesman Rich Johnson said. "They then turned around and landed safely."

At least four people were treated for respiratory distress, firefighters said.

The Houston-bound plane took off shortly before 9 a.m. local time and immediately returned to the San Antonio airport. The plane landed away from the main terminal and firefighters wearing hazardous materials suits entered the aircraft.

"They did not want to bring it back to a gate, just because of the strong odor," Johnson said. "They're not sure what it is, so as a precaution they are taking it out to a ramp area."

Firefighters said there were 151 people on board the plane. It was not immediately clear how serious the injuries were. One person was taken to a hospital, and the other three were being treated on the scene, officials said.

"There was an unknown substance on board," San Antonio Fire Department spokeswoman Deborah Foster said.

Johnson said the incident involved Continental Airlines Flight 07, a daily flight from San Antonio to Houston Intercontinental Airport.

The cause of the odor has not yet been determined.

(Editing by Corrie MacLaggan and Greg McCune)