THE fugitive bombers who bungled their attacks on London’s transport system last week returned to their secret cache of explosives to rearm themselves for another assault, Scotland Yard believes.

Immediately after the bombings up to three of the men who tried to blow up three Tube trains and a bus were seen by a neighbour at the ninth-floor flat in New Southgate, North London, that they were using as a bomb factory.

Witnesses claim that some of the suspects made a second trip the next day to the flat where police yesterday found chemicals and bombmaking materials.

The men who lived at the flat, Muktar Said-Ibrahim, 27, who tried to bomb a London bus, and Yasin Hassan Omar, 24, the Warren Street attacker, were described by a neighbour who met them as looking “startled and dishevelled”. They fled shortly before police established last Friday that the flat had been used as a base.

It emerged last night that Ibrahim, 27, was granted a British passport despite a criminal record for violence. It also emerged that his parents identified him to police after CCTV pictures of him were released.

He was jailed by Luton Crown Court for five years when he was 17 for being part of a gang that carried out a series of muggings at knifepoint at Hertfordshire railway stations. One former friend said that he turned to radical Islam while in prison.

He qualified for early release in 1998 and is then alleged to have met Richard Reid, the jailed “shoe bomber”, at two London mosques. Reid, who was also a petty criminal, tried to blow up an airliner over the Atlantic in 2001.

Immigration officials disclosed that Ibrahim and Omar came to Britain as child refugees. Omar came from Somalia as a 10-year-old in 1992.

Ibrahim arrived with his parents in the same year from Eritrea, aged 14. Barely ten months ago, he swore allegiance to the Crown when he became a British citizen. Police are investigating how he was granted citizenship with a criminal record. A key condition for naturalisation is that applicants should be “of good character”. Officers also want to know if he applied for citizenship in order to obtain a British passort.

Nothing has been seen since of the would-be suicide bombers and police believe that they are being sheltered by supporters in London. They fear that they will break cover only to strike again.

Passport checks have been reimposed for everyone leaving the country in an attempt to prevent the four suspects from fleeing abroad. Controls were imposed after the first wave of bombings on July 7 and were back in place only four days after being lifted.

As Britain’s biggest manhunt went into its sixth day, detectives confirmed to The Times that they are convinced that a fifth bomber is on the loose. He is believed to have discarded his bomb in a park near Wormwood Scrubs prison. Scientists say that it contained the same type of explosives as those used in the botched attacks.

Detectives found “a substantial amount” of explosives in the towerblock at Curtis House, in bins and in a lock-up garage on the estate.

So much explosive has been discovered at different sites since the original July 7 attacks that killed 52 people, that police cannot be sure how much the cell possesses.

Armed police seized a car used by one of the bombers, which was found abandoned a few miles from the council flat that Ibrahim and Omar shared.Streets near the North Circular Road in East Finchley were sealed off as bomb disposal teams searched the white Volkswagen Golf.

Police told how Ibrahim was identified by his own parents. His family spoke of their shock at discovering their son’s involvement in terrorism and condemned his actions. “We are a peaceful family, having lived in this country since 1990,” a family statement said.

Police are still checking identifications of the other two men who took part in the attacks.

Sir Ian Blair, the Metropolitan Police Commissioner, said that senior officers had come close to allowing officers to fire on terrorist suspects seven times since the July 7 bombings. They had been asked to assess the risk of a terrorist 250 times in the past 20 days.

Doctors in London have been asked by police to alert them if they are consulted by any “young men of Asian appearance” with back injuries.

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