Structural engineers who have been working almost round the clock since the explosion declared that eleven flats out of a block of 80 were unsafe after plaster was dislodged and internal walls were shifted by the force.
The local authority, Tower Hamlets, had managed to rehouse several of the families yesterday, but were seeking the assistance of neighbouring councils to provide accommodation.
Last night it was not clear whether the badly damaged flats in a group of six blocks could be saved and refurbished or would have to be demolished and rebuilt at a cost of hundreds of thousands of pounds.
All eighty flats in the Lantern House complex were evacuated on Tuesday afternoon just as John Gummer, the environment secretary, began a visit to see the extent of the devastation caused by Friday night's bomb.
Most of the families living in the bedsit flats and four-bedroomed maisonettes were allowed to return after a few hours once the engineers had completed inspections.
However, 17 families had to spend the night in hotels and temporary accommodation though six were eventually allowed to go back to their homes.
Those not allowed to return had been unable to do so because of fears plaster-work or ceilings might collapse.
Sixty council staff assisted by 10 contractors have been working in shifts around the clock to clear the broken glass and board the shattered windows in other damaged properties.
Builder's Group publishing director Pam Barker said she understood their building was structurally unsound. "The borough surveyor was in there and basically condemned the building," she said.