The family of a Christchurch man missing since his house burned down in suspicious circumstances four days ago are worried for his safety.

Mystery surrounds the disappearance of 40-year-old Michael Croucher last seen by Tilford St neighbour at about 5pm last Wednesday.

There was a fire at Croucher's home Wednesday night, which police said they were treating as suspicious.

Police earlier said there was no evidence to suggest he was caught up or injured in the fire.

Croucher's family was very concerned for his welfare and wanted to know he was safe.

On Saturday police confirmed Croucher was still missing and his absence was out of character. Officers were still investigating the cause of the fire.

They had not had any confirmed sightings, despite widespread media coverage which included photos of Croucher, and police said they had "continuing fears for his safety".

"Police are making efforts on a number of fronts to locate him," a spokeswoman said.

"We ask that anyone with information regarding his whereabouts please contact us, or that Croucher himself make contact with police or family if he is able."

Croucher's family declined to speak to the media.

But his father Glen Croucher wrote on the police missing person post: "Mike just knock on the door. We will help sort things out with you. Love you."

His sister Danielle Croucher appealed on Facebook for sightings.

"Can everyone please keep a look out for my brother when driving or walking around Christchurch and private message me if you see him. He hasn't been seen since Wednesday 5pm, we just want him home safe. Thanks in advance."

Croucher was an avid cyclist and was known to use three bikes in and around Woolston.

People who have seen Croucher are encouraged to contact police on 03 363 7400.