A cache of gas canisters is being guarded this evening after police made two further arrests under the Terrorism Act.

The raid on an industrial estate in Blackburn came as police close the net on an international ring suspected of planning the failed attacks in Glasgow and London.

Gas canisters, nails and petrol were discovered in the vehicles involved in the attempted car bombings.

Locals tipped off police about two deliveries of canisters made to a warehouse, but Lancashire police say it is too soon to say whether the arrests are connected to the wider anti-terror investigation.

Links began to emerge today between doctors from around the world who are suspected of planning the car bombings, attempted in the UK this week.

Last night an Indian doctor in Australia became the eighth person to be held in connection with the investigation, it is believed that all of these suspects have links to the NHS. Before he moved to Australia, Dr Mohammad Haneef worked in the same Cheshire hospital as a suspect arrested in Liverpool on Sunday.

Detectives now believe they have arrested the core of the terrorist cell planning death and destruction in London and Glasgow and are beginning to delve into their backgrounds.

The operation was kick-started by mobile phones found in the cars that were intended to explode in London’s West End. Traced calls led detectives to Glasgow even before the attack on the airport.

Denis O'Donnell, manager at Paisley Cab Company, said he spoke to police about the suspect Bilal Abdulla 25 minutes before he is alleged to have taken part in the Jeep attack.

"The officers just wanted to know how many times Abdulla had taken our taxis and to what addresses," said Mr O'Donnell. "They said it was very important but never said why."

Dr Abdulla, an Iraqi-born doctor at the Royal Alexandra Hospitaln in Glasgow, used the cab firm frequently according to staff. They say he also called a taxi to take him to Glasgow Airport at 7pm on Wednesday 13 June - two and a half weeks before the attack.

All four of the suspects apprehended in Scotland, including Dr Abdulla, have been linked in unconfirmed reports to the Royal Alexandra Hospital. Men arrested in Liverpool and Australia worked at the Halton Hospital in Runcorn, Cheshire, while Dr Mohammad Asha worked as a doctor in Stoke-on-Trent and his wife was a trained medical laboratory technician.

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