One of the four bombers who attacked the London transit system was the object of an MI5 threat assessment last year -- and passed, says a British newspaper report.

The Times of London cited a senior government official in a report published Sunday on its website.

Mohammed Sidique Khan's name was linked to a suspect in a 2004 plot to detonate a 600-pound truck bomb outside a London nightclub.

But MI5 -- the agency responsible for domestic security -- officers decided Khan was only "indirectly linked" to one of the suspects.

On Friday, two U.S. intelligence officials said Khan was known to Mohammed Junaid Babar, a Pakistani American. Babar has admitted setting up terror training camps in Afghanistan -- and had been involved in planning terror attacks on Britain.

On Thursday, Babar -- who pleaded guilty in 2004 to providing material support to al Qaeda, but is now co-operating with authorities -- identified Khan in a photo, saying he had met the man in Pakistan.

There are other reports of possible intelligence breakdowns.

The Observer newspaper is reporting that Pakistani intelligence officials told their British counterparts about possible attacks in Britain.

British intelligence is also under fire for not monitoring an al Qaeda operative who arrived in the UK a month before the attacks and left the night before the London bombings.

The growing investigation

Authorities on at least three continents widened investigations into the London bombings as the death toll rose to 55.

More than 700 were injured when four bombs rocked the city's transit system, hitting three subway trains and one double-decker bus.

Investigators believe four men with backpacks took a train from Luton station, about 50 kilometres north of London, to King's Cross station on the fateful morning, where they went separate ways to carry out the bombings.

On Saturday, authorities released an image captured by surveillance cameras showing four men boarding a train at Luton.

Meanwhile, police in the northern city of Leeds searched an Islamic shop and the home of an Egyptian biochemist.

Magdy el Nashar has been detained in Cairo, after investigators reportedly found traces of explosives in his bathtub. But Egyptian officials say Nashar has no link to al Qaeda. British investigators still wish to interview him.

The investigation into finding the masterminds behind the bombings focused attention on the suspects' ties to Pakistan.

Metropolitan Police Commissioner Sir Ian Blair said police were investigating whether any of the four suicide bombing suspects had ties with Pakistan-based cells of al Qaeda.

In Pakistan, authorities in Islamabad said they questioned students, teachers and administrators at one of two religious schools believed to have been visited by one of the suspects.

Possible Canadian link

Meanwhile, British police are reportedly investigating a possible Canadian link to the London bombings that killed dozens and wounded hundreds.

Momin Khawaja, 26, was arrested more than a year ago in Ottawa and is awaiting Canada's first-ever trial under the new anti-terrorism act.

The courts denied Khawaja bail after authorities charged him with involvement in a conspiracy to bomb British residents in 2004.

"I believe he is innocent until he has been proven guilty," said his father Mahboob.

The RCMP have said they picked Momin Khawaja up in connection with the arrest of nine British residents of Pakistani heritage after he travelled to London in early 2004.

According to The Globe and Mail, British prosecutors say Khawaja met with some men in a London Internet café and was allegedly discussing suspicious things.

"The British believe the same recruiter and explosive designer were involved in both plots," said security analyst John Thompson.

According to the National Post, London bombing suspect Mohammed Sidique Khan may have been associated with some of the men arrested in and around the British capital in 2004.

'Evil ideology'

On Saturday, Prime Minister Tony Blair said authorities were facing an "evil ideology" in their struggle against Islamic terrorism.

"The greatest danger is that we fail to face up to the nature of the threat that we're dealing with," he said during a speech in London.

"And what we are confronting here is an evil ideology. ... It is a battle of ideas, of hearts and of minds, both within Islam and outside it."

The friends of at least two of the suicide bombing suspects have suggested they were angry over the British military presence in Iraq.

But Blair insisted there was no link between Islamic terrorism and the situation in Iraq, where Britain is the second-largest partner in the U.S.-led coalition.

With a report from CTV's Denelle Balfour