AN OFFICIAL investigation was underway today after a suspected chemical leak led to four workers being rushed to hospital with breathing difficulties.

Emergency services – including a hazardous area response team – rushed to a water treatment company in Billingham, Teesside, just before 11.30am yesterday after receiving a "Red 2"-class call - meaning a potential threat to life.

It is understood that some kind of chemical reaction took place within container being unloaded at a warehouse at Biochemica UK, on the Cowpen Lane Industrial Estate.

A delivery was being unloaded, but two of the chemicals reacted with each other inside a container, and caused a release. The building was evacuated and the emergency services called.

Two ambulances and two vehicles from the hazardous area response team were dispatched to the scene, which Cleveland Fire Brigade and police also attended.

The ambulance service spokeswoman said: "Four people have been taken to hospital with breathing difficulties to North Tees Hospital."

A spokeswoman for Cleveland Police said officers attended the scene amid reports of a "suspected chemical leak".

However, police were stood down after it became clear that the chemical leak was contained within the site. One fire crew remained on site as a precaution into the afternoon.

A statement released by the company said: "During a routine delivery procedure there was a minor incident at our Billingham warehouse.

"In line with our procedures the emergency services were notified and attended site as a consequence. There were no serious injuries and those affected have attended hospital for precautionary checks.

"The situation was dealt with internally to the satisfaction of the attending services and normal operations have resumed.

"A full investigation is underway and further information will be issued when available."

A spokeswoman for the Health and Safety Executive confirmed that initial inquiries were being made, and officers would be visiting the site to conduct an investigation.

Biochemica UK is the UK's largest independent water and wastewater treatment specialist. It was founded in 2007 and now operates nationally and in Ireland, with its sights set on international growth.