Train services faced disruption and around 250 homes were being evacuated today following a blaze involving acetylene cylinders at an industrial unit.
A 200m cordon was put in place as six fire appliances and an aerial ladder platform tackled the incident at its height in Friar Walk, Worthing, West Sussex, from just before 2am.
The unit was being used as a vehicle recovery business and the fire involves one truck, tyres, diesel and welding equipment, plus acetylene cylinders.
"This type of cylinder is highly volatile when involved in fire and can explode even when being cooled," a spokesman for West Sussex Fire and Rescue Service said.
A temporary rest centre has been opened by Worthing Borough Council at the Durrington Leisure Centre for people being asked to leave their homes.
Coaches were being laid on to transport people to the centre, while others chose to stay instead with friends and relatives, the fire service spokesman said.
He added that disruption was being caused to rail services between Worthing and Littlehampton, with stations affected including Angmering, Goring, Durrington and West Worthing. Alternative transport is being provided for travellers.
Rail operator Southern said cancellations and short-notice timetable changes should be expected by commuters in the area this morning.
The cordon could remain in place until at least 5pm this evening when it will be reassessed but may be kept for up to 24 hours.
A spokeswoman for Sussex Police said the fire had been extinguished but the cylinders remained a hazard.
A bus replacement service is in operation for passengers affected by the rail closures.
Chief Inspector Kevin Jenkins said: "We are working together with partner agencies to minimise disruption, open the roads and rail service and return people to their homes as soon as we possibly can."