Rail blasts 'almost simultaneous'

LONDON, England (CNN) -- A string of bombs that ripped through three London Underground trains went off within seconds, authorities said, adding that the blasts were so strong none of the victims have been identified.

Technical data and witness accounts suggest the bombs contained synchronized timing devices and were probably not triggered by suicide bombers, Deputy Assistant Commissioner Brian Paddick told reporters Saturday.

"A slightly different picture is emerging around the timing of these bomb incidents," Paddick said, revising original accounts that the train blasts occurred over a 26-minute span Thursday morning.

"All three bombs on the London Underground system actually exploded within seconds of each other, at 8:50 in the morning," he said. Nearly an hour later, at 9:47 a.m., a fourth explosion tore through a double-decker bus.

"It was bang, bang, bang, very close together," London Underground managing director Tim O'Toole said of the train blasts. (Timeline )

More than 50 people were killed and 700 injured in the rush-hour blasts. Scotland Yard Commissioner Ian Blair said the total death toll would rise, but probably not above 100.

Authorities have vowed to hunt down the bombers