London — Up to five potential suicide bombers may be at large in Britain, the security services admitted last night after the convictions of three British Muslims accused of plotting the world’s biggest terrorist atrocity.

The Al Qaeda terrorists planned to cause carnage by detonating liquid-based bombs disguised as soft drinks. They had recorded suicide videos in which they promised “body parts” would be scattered on the streets.

The police and MI5 believed the extremists wanted to cause an “unprecedented” loss of life with simultaneous suicide attacks on several transatlantic airliners bound for America.

The arrest of the gang in 2006 led to permanent restrictions on liquids being carried in hand luggage.

But a jury was unable to agree on whether Abdulla Ahmed Ali, Assad Sarwar, and Tanvir Hussain had decided on specific targets and instead they were convicted of conspiracy to murder “persons unknown.”

Four other men are likely to face a retrial after the jury failed to agree on whether they were part of the plot. Police admitted last night that up to five would-be bombers may still be on the loose, as a bugged conversation between the plotters in their east London bomb factory disclosed that they had recruited up to 18 people.

To date, only 13 people have been arrested in connection with the plot.

Senior officers believe the “key players” have been rounded up, but admit that they would be “unwise” to suggest that there were no more terrorists connected to the gang.

The police were forced to move in early to arrest the gang after a jittery President Bush put pressure on the Pakistani authorities to arrest their Al Qaeda contact in Pakistan.

MI5 — which had been watching Mr. Ali since 2004 — had hoped to continue gathering intelligence on the remaining members of the cell, but their hand was forced by the American intervention.