Police have launched a city-wide hunt for the gun used in the cold-blooded murder of a Bradford taxi driver.

Detectives said the firearm - possibly a modified replica or adapted gas-powered air-gun - exploded in the killer's hand as he calmly shot Mohammed Basharat in the head in front of colleagues at a taxi office.

After recovering fragments of the weapon from Little Horton Private Hire in Holme Top, they called for the public's help in tracing the damaged body of the weapon.

A specially-trained sniffer dog was called in yesterday as officers scoured wasteland by a row of four houses in Greaves Street, Little Horton, just a few hundred yards from where Mr Basharat was murdered.

Detectives said two Afro-Caribbean men they want to question had fled from the properties shortly before a police search was carried out and crack cocaine, cannabis, personal belongings, documents and drugs paraphernalia were recovered.

Father-of-four Mr Basharat, 33, was shot twice in the head by a masked gunman who walked into the cab office at around 8.10pm on Saturday. Police say the day before, he had been involved in a minor road accident with a hired car containing two Afro-Caribbean men in Park Lane at the junction with Holme Street. Mr Basharat had grappled with the driver who shouted he would kill him as he fled the scene.

Detective Sergeant Colin Stansbie said: "At the time of the shooting, the gun basically exploded in the assailant's hand. He fled with whatever was left, which would then have been useless. This may have been discarded around the Greaves Street area where our inquiry has focused. Someone may have come across it and thought it was the remains of a toy gun or something totally innocent."

While the murder weapon might have been a genuine handgun, it is believed it could have been a modified replica or a gas-powered air-gun adapted to take .38 calibre bullets.

Det Sgt Stansbie said: "It is vital that we recover this weapon and we would call on anyone who finds it to contact us immediately."

He said the killer probably injured his hand firing the weapon and he asked anybody who recalled someone with similar injuries to contact him.

Anyone with information can contact the freephone incident room on 0800 318001.