At least nine people needed medical treatment after a 'chemical reaction' in a toilet caused poisonous fumes to fill a Barrowby property.
Two fire crews from Grantham were called to reports of a smoke-logged building in High Road just after 4pm yesterday.
A Lincolnshire Fire and Rescue spokesman said: "The fumes were caused by a chemical reaction between toilet blocks and domestic bleach.
"Fire and rescue used two breathing apparatus and one hose reel to remove the toilet blocks and flush away."
Firefighters gave four casualties oxygen and nine were treated at the scene by ambulance crews.