Nearly 100 firefighters are trying to put out a major blaze at a food factory near Hull.
Workers on the night shift at Geest's food factory in Barton-upon-Humber have been led to safety.
Fire officers say they are worried about toxic fumes which are now drifting from the badly damaged plant across the river to Hull.
Humberside Fire and Rescue Service is warning people in the area to keep inside and close all windows and doors.
The fire started at 2232 BST on Sunday on the industrial estate in Antelope Road.
A fire service spokesman said: "We would possibly have had to evacuate the town if it was not for the weather conditions taking the smoke across the river.
"It appears we have been fortunate, but we are concerned the smoke is heading towards Hull and we advise householders to close their windows and doors.
"We don't think the fumes are particularly dangerous but they are a bit nasty."
The main part of the fire is in the packaging warehouse where insulation panels of polystyrene are thought to have triggered the toxic fumes.