The shed fire that killed Queensland father Todd Mooney and his 10-year-old daughter Kirra is believed to be deliberately lit and involved a third party, police say.

Remains believed to be the 54-year-old man and the girl were found after the blaze at Biggenden, south-east of Bundaberg, on December 20.

Investigators now believe the pair were killed, rather than the fire being accidentally sparked.

“A crime scene was declared and following scientific examination, investigators believe the fire to be deliberately lit,” police said in a statement on Thursday.

Wide Bay Burnett District Detective Chief Inspector Gary Pettiford said State Emergency Service volunteers would examine a paddock near the shed for further evidence on Thursday.

“We’re looking for anything, whether it be a firearm or a knife, anything unusual that may have been thrown into the grass … we believe there is a third party involved but I can’t comment further on that,” Detective Pettiford said.

He said emergency services were called to the property at 12.20pm to respond to a fire with two residents unaccounted for.

“It took quite a while for police and emergency services to put the fire out and then the building and the whole structure were terribly unsafe; they had to be stabilised before any searches could be made of the shed area; the house was unaffected by the fire,” Detective Pettiford said.

Police found the remains of two bodies in the shed. They have completed forensic examinations of the structure in recent days, including hand-sifting debris and removing asbestos, with the help of fire investigators and a pathologist.

The investigation has yet to find the origin point of the fire or identify an accelerant but autopsy results steered police to treat the incident as a homicide.

“Originally we thought this was a terrible, tragic accident,” Detective Pettiford said

“We haven’t been able to formally identify the remains as yet through DNA or dental records. We do believe the remains are those of the residents.

“As a result of all the forensic investigations, we have now reached a conclusion where this hasn’t been a tragic accident … it’s gone from a terrible tragedy to a horrific homicide involving a little girl and her father.”

Police have called for anyone with information, or CCTV or dashcam footage, particularly from anyone travelling between Biggenden and Mundubbera on December 20 between 10am and 2pm, to contact them.

The local bakery owner and his daughter are survived by his fiancee Bec Hansen. She was reportedly due to marry Mr Mooney on Wednesday.

Callide MP Bryson Head paid tribute to Mr Mooney and Kirra three days after the fire.

“There is no doubt that Todd was a great man with a brilliant work ethic and a passion for baking,” he wrote on Facebook.

“He supplied a number of surrounding towns with fresh pies, bread and other baked goods. This loss will be felt far and wide across the Wide Bay and Burnett.”

-AAP