Residents have been warned to stay indoors with their windows closed after a chemical leak caused a cloud containing hydrochloric acid to form over West Thurrock in Essex.
Thurrock Council recommended that schools in the area remain closed on Tuesday as a precaution to prevent pupils from being exposed to fumes which can be a “minor irritant”.
The fire service received reports of a cloud of fumes on Monday afternoon following a reaction involving a cylinder at an industrial site in Stoneness Road.
Firefighters are working to establish what chemicals were involved.
Neil Fenwick, area manager at Essex County Fire and Rescue Service, said: “We understand that the cloud includes an amount of hydrochloric acid.
“A 100-metre exclusion zone was created at the site as a precautionary measure.
“We now know that these fumes were caused by a tank that has failed, the leak is contained to within the site.
“Firefighters are now safely managing the leak and this process is expected to continue for some time.”
The fire service is supporting the industrial site’s management team by supplying a large quantity of water which will dilute the product.
It is expected that this will suppress the cloud, the fire service said.
An Environment Agency spokesperson said: “We have been supporting the emergency services and Health Protection Agency to respond to a large chemical spill in Thurrock.
“We have deployed Air Quality Monitoring equipment overnight to support the Health Protection Agency.
“This is a regulated site, which means it is subject to regular monitoring and inspections.”
Public Health England has advised residents to remain inside with doors and windows closed, and drivers are advised to keep their air conditioning off.
Those with existing respiratory problems have been urged to keep medication with them and call 111 if they feel unwell.