A mum and her three month old baby are in hospital after a fire at the Red Lion Inn pub in Brixworth.
Engines from The Mounts, Moulton and Mereway were called to a fire in the ground floor of the Harborough Road pub at 6.20am on Thursday morning.
A woman and her baby were among the people who were upstairs when the blaze started and managed to escape and are said to be relatively unharmed.
A 33-year-old man has been arrested on suspicion of arson and is helping officers with their enquiries.
The pub, which has been severely damaged by heat smoke and flames, is now being treated as a crime scene.
Luke Hodson, a fire investigator, said at the scene this morning: “Firefighters had to break down the front door to get in and there was smoke and flames issuing from the windows to the right of the doors.
“We did a search of the building, but we were quickly satisfied there was nobody still inside.
“However a woman and her three-month-old baby were taken to hospital as a precaution. In an infant of that age, their lungs are not fully developed so there can be severe problems. They were our main priority.”
The fire started in the bar and lounge area and firefighters put out the flames within 20 minutes and managed to get the building under control by 7.45am.
Harborough Road from the just before the Red Lion to just after the George Inn pub has been cordoned off.
Scenes of crime police officers and the fire service are expected to be at the pub all day, possibly into tomorrow as they try to establish how the fire started.
Mr Hodson said: “If we don’t have an obvious cause, we’ll work with the police to try to find one, which is standard procedure.”