Police are searching for a man after a suspicious fatal house fire in Sydney’s Inner West overnight.

Just after 4am, emergency services were called to Irrara Street, Croydon, after reports of a fire.

Crews extinguished the blaze, which badly damaged the home and caused the roof to collapse.

The body of a person was found inside.

They are yet to be formally identified, but police said the body is believed to be that of an 80-year-old man.

Investigators said the cause of the fire was unknown, but it is being treated as suspicious.

It was earlier reported that another person at the home remained unaccounted for as firefighters searched the property.

Police have now put out an appeal to find a man who lived at the home and detectives are investigating under Strike Force Leverier.

He is described as being of Caucasian appearance, aged in his 50s, of large build, about 190cm tall, with short, brown hair.

Authorities suspect that the individual might be utilizing public transportation and could be moving through regions such as the Inner West, Circular Quay, Watsons Bay, and nearby locales.

Anybody with information as to his whereabouts is urged to contact Crime Stoppers on 1800 333 000.