According to the Associated Press, the blast and ensuing fire forced the evacuation of residents in a 1-mile radius around the scene.
Three firefighters were hurt when they attempted to put out the chemical fire with water, causing an explosive reaction, according to the Laredo Morning Times.
The driver of the Key Energy Group tanker was also injured, along with the train’s engineer and conductor.
Officials said the tanker truck did not yield to the westbound train.
The accident occurred just outside the small town of Aguilares, which is about 25 miles east of Laredo.