An explosion has ripped through the Conoco oil refinery on the Humber estuary.
The fire service says the blast at the South Killingholme refinery near Grimsby involved large quantities of petroleum gas and petrol.
Around 50 firefighters are at the scene alongside police and ambulances. No details of any casualties have been released.
Witnesses report seeing flames shooting into the air and residents are being advised to stay indoors.
It is unclear what the cause of the blast was.
Last month Conoco, which is one of the world's largest energy producers, found itself targeted by environmental protesters.
Nine Greenpeace protesters spent the night on Conoco Jet's oil exploration rig in the North of Scotland.
The demonstrators secured themselves to the semi-submersible rig in opposition to Conoco Jet's alleged failure to use green fuels.
Greenpeace say the protest stopped the rig from moving for 24 hours and helped publicise their case.
However, Conoco Jet say the protesters' actions were dangerous and irresponsible.
Police detained 17 demonstrators as they tried to board inflatable boats at Nairn Harbour in the Moray Firth.