Police remained at a murder scene in Thetford on Friday night.

Eastern Daily Press: Police at the scene where a man is believed to have been stabbed at Brandon Road in Thetford. Picture: DENISE BRADLEYPolice at the scene where a man is believed to have been stabbed at Brandon Road in Thetford. Picture: DENISE BRADLEY (Image: Archant)

Brandon Road remains cordoned off and a white police tent could be seen earlier in the evening.

Four men have now been arrested after the victim, a man thought to be in his 20s, died at the roadside on Thursday.

Officers who were on patrol in the area discovered members of the public providing first aid to a man, who had received stab wounds, on the side of the A134 Brandon Road shortly after 7pm.

Police have said they are dedicating "considerable resources" to the investigation as they revealed they had launched a murder probe.

On Friday evening, many people were clearly in shock at discovering what many had initially thought was a car crash had turned out to be a murder inquiry.

David Ross, 39, from Castleford Close, off Brandon Road, Thetford, said they had seen the "flashing lights" and had thought it was a car accident.

But he said they had subsequently heard the victim had been "stabbed five times in the neck".

He said he had heard the victim had been attacked near Blaydon Bridge and had got up to near Brandon Road where he "collapsed on the floor".

MORE: Thetford murder: Members of the public battled to save victim's life

His wife, Sarah Ross, 44, said: "There was a group of about 20 young lads saying 'he's got stabbed, he's got stabbed.

"Police took a phone off one young lad who was videoing it.

"There was just people saying "he's been stabbed, but no-one believed them."

A 31-year-old woman from Brandon Road, who wanted to remain anonymous, said she had been out but returned to see "everything going on".

She said there were about 50 people out in the road, many trying to help.

A 38-year-old woman, who did not want to be named, said she thought there had been a crash after seeing the air ambulance near the scene.

The woman, who did not want to be named, said: "I didn't know until Friday morning that someone had been stabbed, I just assumed it was a crash.

"It was a shock to find out what it was."

Another woman, from nearby St John's Way, off Brandon Road, said she was "shocked" adding that "things like that don't happen around here".

Norfolk Police has set up an online information portal as part of the investigation.

The portal has been set up so people can share information with detectives from the Joint Norfolk and Suffolk Major Investigation Team who are now treating the man's death as murder.

Four men have been arrested in connection with the death and remain in custody.

Detectives believe this to be an isolated incident with those involved known to each other.

Any witnesses or anyone with information that may help the investigation can share information with the Joint Norfolk and Suffolk Major Investigation Team.

They can also telephone Norfolk Police on 101 and quote reference Operation Petersfield and a member of the enquiry team will call them back. Alternatively, they can contact Crimestoppers anonymously on 0800 555111 or online.