Almost 100 children were forced to miss important GCSE and A-level exams after a major fire at an industrial packaging site engulfed a town in smoke this morning.
As many as 180 people were evacuated from homes beside the Skymark plant on Southern Avenue in Leominster, Herefordshire, while five schools in the area were also shut.
A 400-yard cordon was set up around the blaze, which sent up a plume of black chemical smoke, and neighbouring residents were evacuated to the nearby Bridge Street sports centre.
Around 1,400 children at Leominster Primary, Leominster Junior, Minster College, Westfield Special School and The Priory Pupil Referral Unit were affected, with about 90 at Minster College stopped from sitting exams, Herefordshire Council said.
A pall of black smoke rose up above the Skymark factory, which stores paints, solvents and plastics, and other people whose homes were caught up under the smoke were advised to remain indoors with windows shut.
It is not yet known what caused the fire, but fire crews have identified one chemical involved as isocyanate, which is commonly used in vehicle paint and can cause asthma.
A number of explosions occurred after emergency services were called to the premises at around 3.30am.
A spokesman for Hereford and Worcester Fire and Rescue Service could not say whether the "minor bangs" had been caused by butane canisters known to be at the site.
He said: "We are tackling the fire externally and we certainly haven't sent any fire crews inside yet because of the clear dangers."
The spokesman added nobody was thought to have been killed or injured in the blaze.
A spokesman for Herefordshire Council said the number of people received at the Bridge Street Sports Centre had reached between 170 and 180.
Fire officials said that number could rise slightly throughout the day as residents attempting to return to smoke-covered homes are being redirected to the centre.
The minor injuries unit and outpatients departments at Leominster Community Hospital were shut this morning, with anyone suffering minor injuries advised to go to the Accident and Emergency unit at County Hospital in Hereford.
Environment Agency chemical experts were at the scene on Southern Avenue and officers from the Met Office were helping with tracking wind direction as the chemical cloud drifted over the town.
A police spokesman said the wind "remained static" but could increase later, causing the smoke to rise higher and dissipate.
The fire service spokesman added: "There are a minimum of 85 firefighters at the scene and a very considerable number will be here all day and into the night."
A Hazardous Area Response Team (HART) was dispatched and deployed with oxygen cylinders, a West Midlands Ambulance Service spokesman said.
He added: "The concern relates to the smoke coming from the fire.
"A number of people have been taken to the leisure centre in Bridge Street. Ambulance crews helped to evacuate an elderly wheelchair-bound couple and an elderly woman from their homes."
Minster College was making efforts to ascertain from the exam boards what would happen to the pupils who missed exams today, a spokesman for Herefordshire Council said.