The family of a Birmingham man arrested in Thursday's terror raids last night spoke of their fears for his health as it emerged his brother - also a suspect - was wanted by police in connection with a separate murder inquiry.

Relatives of Tayib Rauf described the family's worries as authorities in Pakistan said they had detained Rashid Rauf and six others, including another British national, in Karachi and Lahore. Officials in Pakistan identified Rashid Rauf as a "key person" with ties to al Qaida.

The arrests were in connection with the alleged plot to blow up transatlantic passenger jets in mid-flight, which paralysed Britain's airports on Thursday.

A West Midlands Police spokeswoman would not comment on the details of the British investigation into Rashid Rauf about five years ago, but said: "The investigation was never concluded. Lines of inquiry are ongoing."

Tayib was arrested at his home in Ward End in Birmingham on Thursday morning. He was among 24 people detained across the country and one of 19 whose assets were frozen yesterday by the Bank of England under anti-terrorist legislation.

His father, Abdul Rauf, is in Pakistan for a relative's wedding while his distraught mother and sister were staying with other relatives in Birmingham.

Last night Tayib's great-uncle, Qazi Amir Kulzum, described the 22-year-old as deeply religious, and said his arrest had shocked relatives and friends.

"They are a very honest, religious family. Tayib is disabled, he lost his hearing in one ear because of a childhood sickness.

"He is very, very polite, the kindest person you could hope to meet. He helps his father delivering cakes and confectionery, he prays five-times-a-day, he has been to Mecca on pilgrimage. No one can believe that he would be involved in such matters.

"We are all in shock and worried about his welfare. I'm worried about the strain he's under and fear he might have a heart attack.

"His mother's in shock. She's unable to walk as she has problems with a leg, I think she's had a stroke in the past and has been in hospital. She's a very devout Muslim, she teaches children and she has worked over the years to get her children private education."

Mr Kulzum said he had not seen Rashid for years and was not aware of his case or his arrest in Pakistan.

Abdul Rauf, in his 50s, came to Britain from the Mirpur district of Pakistan several decades ago. His four sons - Tayib, Rauf, Asim and Hamza - and one daughter were all born in Britain.

"They are all very religious and what has happened to them, especially Tayib, has been very depressing for all of us," Mr Kulzum added.

Foreign and Commonwealth Office officials last night said they could not reveal any details of Rashid Rauf's background, or indeed, confirm whether he was a British citizen.

Officials in Pakistan identified Rauf as a "key person" and said the arrests triggered the police operation to dismantle the alleged plot in the early hours of Thursday. Interior Minister Aftab Khan Sherpao claimed Rauf had ties with al Qaida.

"We arrested him from the border area and on his disclosure we shared the information with British authorities, which led to further arrests in Britain," he said.

Pakistani intelligence officials said yesterday that a further ten Pakistanis had been arrested in the eastern district of Bhawalpur, about 310 miles south-west of Islamabad.

The Pakistani Foreign Ministry said there were indications of an "Afghanistan-based al Qaida connection" to the alleged plot.

Meanwhile, Britain's airports started to return to normality yesterday but stringent restrictions remained in place.

Tony Douglas, chief executive of the airport operator BAA, said the restrictions would remain in force for "some time". They were continuing to disrupt flights today although on a lesser scale.

"Until the Department for Transport and British Government revise the status of the security problem, we will be maintaining working to these security precautions," Mr Douglas said.

He warned this weekend was likely to be busy and urged people flying, particularly to the US, to check with their airline before travelling. n One of the people arrested in Thursday's raids was last night released without charge. Scotland Yard refused to identify them.