Two Asian men arrested under the Terrorism Act yesterday after reports that they were taking delivery of ten propane gas canisters were today being questioned about growing cannabis plants.

With the country on its highest alert after the attempted bomb attacks in London and Glasgow a huge police operation was launched when officers were told that the two men could not give “a reasonable explanation” for why they were buying so much gas.

Plain-clothes police officers swooped on the two men, aged 22 and 29, at the Furthergate Industrial Estate in Blackburn, East Lancashire.

Eyewitnesses said a delivery driver arrived at a unit on the estate yesterday lunchtime with about five 47kg bottles and that two Asian men appeared shortly afterwards.

An unmarked police Ford Focus carrying two officers immediately pulled up and the men were arrested under the Terrorism Act 2000.

A second consignment of five more canisters arrived at the premises close to the town centre shortly afterwards.

But when officers ventured inside the large unit they found a “very sophisticated and well looked after” cannabis operation although there were not many plants there as they had already been harvested. Detectives have now ruled out the men having any links to terrorism.

Lancashire Constabulary defended the arrests under terror legislation as “necessary under the circumstances”.

A spokesman said: “Following a search of the industrial premises on Birley Street in Blackburn, police can now confirm that the premises would appear to have been used to cultivate cannabis. More detailed searches of the premises are planned.

“The two men in custody are now being held on suspicion of offences under the Drugs Act, and are not being dealt with under terrorism legislation.

“The men were originally arrested under the Terrorism Act 2000 following information about suspicious activity around the industrial unit.

“Lancashire Constabulary will investigate any information that is passed to us before responding in a proportionate and measured way. We will only act when it is necessary to do so and it was felt that under the circumstances presented to us, that these arrests under the Terrorism Act 2000, were necessary at that time.

“We rely on communities to inform us about any activity that they find suspicious and this incident is a good example of where an individual has become alarmed and has shared the information with the police. That was the right thing to do. While this is no longer a terrorist-related inquiry, it is a criminal one and the men remain in custody."