A man has been arrested on suspicion of arson at flats in a Ceredigion seaside resort in the early hours of Thursday.
The 27-year-old was detained after the blaze at the house in Borth, near Aberystwyth, which had been converted into three flats.
It is understood that two adults and a two-year-old child living in the bottom flat were forced to flee their home as the flames took hold.
Police said neighbouring properties had to be evacuated shortly after 0500 GMT.
Mid and West Wales Fire and Rescue Service said the roof of the property, a former pizzeria, was well alight when two fire crews arrived in Borth High Street.
The top floor flat was gutted by fire said Dyfed-Powys Police, but it was unoccupied because the female resident was staying with her boyfriend.
The road was closed while two crews and a team using an aerial ladder tackled the fire.
A Dyfed-Powys Police spokeswoman said: "The building was well ablaze and neighbouring properties had to be evacuated.
"The street was also closed, as was the Borth road from Clarach half a mile from Ynys Las. The premises was gutted and a neighbouring property was severely damaged. A 27-year old man has been arrested on suspicion of arson, and remains in custody at present."
Fire fighters had to remove loose and unsafe tiles from the roof of the property and some from a neighbouring house.