Police investigating the homicide of a Sri Lankan man in a north Canterbury town say he died before a house was deliberately set on fire.

The body of Sameera Chandrasena, 28, was found in the house on Domain Rd, Oxford, on Thursday after neighbours reported the fire about 4am.

A post mortem revealed he died of injuries consistent with an assault either late on Wednesday or early on Thursday, Detective Inspector Virginia Le Bas told NZ Newswire.

Two Sri Lankan men have been arrested on charges unrelated to the death.

One man has been charged with assault and has been remanded in custody until March 5 and the other man is being detained on immigration matters.

Mr Chandrasena knew the men through the Sri Lankan community, Det Insp Le Bas said.

Police expect to lay further charges relating to the death and arson.

Det Insp Le Bas did not want to say if the arrested men had been involved in Mr Chandrasena's death or if anyone else might be charged, because the investigation was in the early stages.

"At this stage I think that we've got a number of inquiries to complete and we need to just consider everything before us before we determine anything and any further charges."

The "difficult" scene examination would take several days, because the property had been badly damaged by the fire, she said.

Police were searching nearby properties for discarded clothing and still needed to speak to a number of Mr Chandrasena's associates and friends.

Det Insp Le Bas believes he was a New Zealand resident.

He had a brother, who was his only next of kin in New Zealand, and she said she understood his body would be returned to his family in Sri Lanka.

It would not be released until after it had been formally identified and cleared by the coroner, she said.