Emergency service crews were called to Pilgrim Hospital, in Boston, this morning to deal with a fire caused by a patient smoking in bed.
The service confirmed that two crews from Boston and one from Leverton were called to the hospital.
They recorded severe damage to bedding.
A spokesman for United Lincolnshire Hospitals Trust confirmed the fire had happened between 6-7am this morning.
They said investigations were ongoing.
No further details available at this time.