A Brentwood school became the scene of a hazard investigation this morning (Thursday) after a chemical spill at 8.40am.

Medical teams treated three members of staff at Shenfield High School, on Alexander Lane, after they inhaled chlorine fumes.

The school’s 800 students were kept in their classrooms as a precaution, and none were harmed.

Police and the Environment Agency were informed about the incident, and the school was back to normal before 11am.

The incident occurred when a 5 litre tank of poly aluminium chloride was unintentionally mixed with chlorine.

A spokesman for Essex Fire and Rescue Service said: “Two high pressure fans were used to clear the swimming pool plant room of the gas and the area is now declared safe”