Police hunting the gangs who tore a city apart in last summer's race riots believe travelling thugs from the North-East may have been behind the violence.

Detectives in Bradford have widened their investigations to Middlesbrough, Darlington and Newcastle after receiving fresh information linking gangs from the region to the trouble.

West Yorkshire Police, who are liaising with colleagues in the North-East, yesterday released 20 pictures of people they believe are responsible for a range of serious offences, including violent disorder.

Police said yesterday they could not rule out that gangs from the region were drafted in last summer as tensions rose in the city.

Detective Inspector Tony Craven, senior investigating officer with the Bradord investigation, code-named Operation Wheel, said: "During the riots there was a hardcore of people committing the most serious offences.

"The people shown here are not just faces in a crowd, they have all committed serious offences and I would appeal to anyone who recognises them to get in touch with us."

About 70 police officers from Northumbria, Cleveland and North Yorkshire were drafted into Bradford at the height of the eight-hour riot on July 7, last year.

Gangs of Asian and white youths fought running battles with officers, who were pelted with bricks, bottles, petrol bombs and fireworks. Officers were also attacked with baseball bats and hammers during violent clashes which saw two people stabbed and scores of cars set on fire.

The riot left 120 police officers injured, caused thousands of pounds worth of damage and left scenes of devastation behind in the city.

West Yorkshire Police have released a total of 212 pictures on 12 separate posters since the riots and 70 per cent of those shown have handed themselves in.

More than 200 people have been charged with a variety of offences including 134 charged with riot, the most serious public order offence in English law.

Police have so far arrested suspects across West Yorkshire and from various areas of Lancashire and Greater Manchester.

Detectives have re-released the picture of 20 suspects they still want to speak to in connection with the riots.

Information received from the local community has been sparse about the 20, leading detectives to believe they may not be from the Bradford area.

Police switched their investigation to the North-East after receiving telephone information that some suspects live in the region.

Said Det Insp Craven: "The poster campaign so far has been extremely successful and the entire community across Bradford has responded superbly.

"However, the 20 people shown here remain unidentified and I now believe that they may be from further afield.

"I would urge communities in the Darlington, Middlesbrough and Newcastle areas to take a close look at these faces."

Anyone who recognises any of the faces from the posters should ring the Incident Room in Bradford on (01274) 376915 or the Urdu-speaking language line on (01274) 376916.

E-mails can also be received at the Incident Room at bradfordriots@westyorkshire.pnn.police.uk