In west Thurrock in Essex hundreds of residents have been told to stay at home with windows and doors to be kept closed after a chemical leak.
A cloud containing hydrochloric acid was seen over west Thurrock on Tuesday and schools in the area remain closed as a precaution.
Essex County Fire and Rescue Service received reports of fumes on Monday afternoon after a reaction to a cylinder at the industrial estate in Stoneness road.
Neil Fenwick of 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.”
Public Health England are advising residents in the affected area to remain indoors and drivers are being told to keep off their air conditioning.
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.”