A FIRE engulfed 40,000 square metres of land in one of the biggest peat blazes in the county in years.
The peat fire on Crowle Moor has swept across thousands of square metres already and could continue to burn for several days to come.
Natural England, the body which owns the land, said the blaze could be the worst in lowland England since 1995.
And bosses there said it could change what species can live on the land forever.
Moorland near Swinefleet peat works is still alight now.
Nick Granger, group manager for the Humberside Fire And Rescue Service, said: “It’s a difficult fire to fight as the ground absorbs the heat, so we can appear to have extinguished it on the surface, but deep down it’s still burning.
“All we can do is dig fire trenches and fill them with water. These incidents can last for days or even weeks.
“It’s not like a house fire you can extinguish in an hour.”
Eight fire engines, a mobile command centre and more than 30 firefighters were at the scene initially.
The firemen had a first strike at the blaze on Sunday night, then retreated as darkness fell and fighting the fire became too dangerous.
One fire engine stayed overnight as a lookout to ensure the fire did not get out of control.
“It’s a pretty big fire,” said Mr Granger. “The wind is blowing the fire underground.
“The fire would spread and spread if left.
“There are areas in America that have been burning for years, so we like to resolve these incidents as soon as possible.”
He said rain would help them immensely.
It is uncertain how the blaze began and investigators are seeking to find the cause of the fire.
“It could have been caused by one of a million reasons,” said Mr Granger.
“It can be kids with matches, or glass bottles that have magnified the sun’s rays. It’s not unknown for sparks from vehicles to cause a fire.
“To determine how this started is virtually impossible.”
The fire put a drain on the service’s resources on a busy bank holiday weekend.
“It’s very labour intensive, with firefighters working with shovels and spades,” said Mr Granger. “We have to balance our services.
“On a bank holiday, we expect severe road traffic accidents.
“This is a fire that needs resolving, but we need to make sure life risk is dealt with adequately.”
Conservationists expressed concern as important species went up in flames.
Kevin Bull, senior reserve manager for Natural England, said: “It’s quite exceptional and it’s been quite devastating.
“The land will heal itself over time, but it will take a long time to do it and it could change the physiology of the area.
“It will affect what species may grow.”
He said his hope was key species, such as birds and deer had escaped when they smelt the smoke, but said heather and cotton grass has been incinerated.