Detectives were today investigating whether a fire which killed a Bradford mum and her six-year-old son was linked to an argument outside their family home two days earlier.

Four Bradford men and a youth - aged 17, 19, 20, 21, and 23 - were questioned in connection with the inquiry. Today a West Yorkshire Police spokesman said all five had been released on bail, pending further inquiries for matters not related to the fire.

They were originally arrested on suspicion of threats to kill.

The spokesman said that no evidence of arson at the scene had yet been discovered, but they were continuing investigations along with the fire service.

Police also appealed for a number of motorists spotted at the scene of the blaze - which claimed the lives of Denise Clough and her son Mark - to come forward.

At 12.20am on Tuesday a fierce fire broke out at the semi-detached house in Broadstone Way, Holme Wood. Although Mrs Clough, 38, and six-year-old Mark Clough were dragged to safety, they were both dead on arrival at Bradford Royal Infirmary.

Two of Mrs Clough's other children, 17-year-old Andrew McC-afferty and 12-year-old Simon Clough, managed to escape the blazing house and were released from hospital after treatment.

Detective Superintendent Allan Doherty, who is leading the investigation, said: "We need to trace a number of vehicles which we know were present or driving past the scene at the time of the fire."

A large dark saloon car wasparked outside the property, possibly as the fire took hold. It is thought those inside it may have helped victims out of the house.

That car was joined by a light- coloured Vauxhall Astra, also parked outside the property.

A small, silver people carrier-style vehicle also stopped close by.

It was thought to contain two men and a woman. This may have been driven off before the fire brigade arrived.

About 50 yards up Broadstone Way, towards Tyersal, a tow truck was parked with a vehicle loaded on a trailer.

Another car is believed to have driven past at the time of the blaze.

Det Supt Doherty said: "We need to know what involvement these had in the incident, if any at all.

"These people could hold information which is vital."

He said if the drivers and passengers were not involved they needed to be eliminated from the inquiry.

Det Supt Doherty said: "These men are being held as a result of information received about an incident which is said to have occurred outside the same address."

While police remained tight-lipped about the precise details, they confirmed it occurred at some point on Saturday afternoon.

The inquiry is now working to establish whether the two incidents are connected.

"I would urge anyone who witnessed anything outside the property on Saturday afternoon or who has any information about these incidents at all to contact us immediately," said Det Supt Doherty.

Officers and forensic experts were set to re-examine the scene yesterday as well as conduct more door-to-door inquiries and interview further witnesses.

Det Supt Doherty stressed it had still not been established whether the fire was arson or an accident.

Anyone with information should contact (01274) 376459.