An investigation into a fire in St Pauls, Bristol, has been delayed as the building was not safe to enter.

Investigators from Avon Fire and Rescue Service were due to enter the property in Wilson Street today to examine the cause of the blaze which started on Sunday afternoon.

The roof of the four-storey building has fallen in as a result of the fire and crashed through the floor below.

Studio rooms at the side of the building were reported to have been severely damaged in the fire.

Crews were called to the blaze at about 4.30pm on Sunday and firefighters remained on the scene overnight.

Others returned to the property – which was the childhood home of the world's first woman doctor Elizabeth Blackwell – every couple of hours yesterday to "damp down" following the blaze.

Avon Fire and Rescue Service said that while the cause of the blaze is yet to be determined, it is not expected to be suspicious.

Investigators were unable to enter the property until there was no sign of hotspots inside.

They also had to wait to be given the all-clear by Bristol City Council structural engineers who had checked the building.

Officials said the outside structure of the building was sound but the inside is not.

A police cordon has been set up on the pavement outside and the owners were advised by the council's structural engineers to board up the doors.

At the height of the fire a turntable ladder was used to tackle the flames from above, along with two 45mm jets and three high-pressure hoses.

Thick smoke and flames billowed from the roof of the building as 25 firefighters on five pumps battled to extinguish the fire.

The fire service received almost 40 calls from the public reporting the fire.

It was out by 7pm and as far as the emergency service was aware, no one was in the building.

Elizabeth Blackwell was born in Counterslip in 1821, the daughter of a sugar refiner and anti-slavery campaigner who had advanced beliefs about educating girls.

She later moved to the house in Wilson Street and the family stayed in Bristol until they moved to the United States in 1832, where Dr Blackwell carried out her training.