A home-made explosive device which blew up in a taxi in Liverpool on Sunday contained ball bearings that could have caused significant injury and death had it detonated in different circumstances, counterterrorism police said on Friday.
Authorities declared the blast a terrorist incident. The bomber died after the explosion engulfed the taxi in flames. The driver, who escaped, was treated for injuries.
"It was made using home-made explosive and had ball bearings attached to it which would have acted as shrapnel. Had it detonated in different circumstances, we believe it would have caused significant injury or death," Russ Jackson, Head of Counter Terrorism Police North West, said of the bomb.
"We still do not know how or why the device exploded when it did but we are not discounting it being completely unintentional and it is a possibility that the movement of the vehicle or its stopping caused the ignition."
After the blast, the UK government raised the terrorism threat level to "severe".
Three men, aged 21, 26 and 29, were arrested in connection with the blast on Sunday and a fourth man aged 20 was detained on Monday.
The bomber was named as Emad Al Swealmeen, an asylum seeker whose case to stay in the UK had been rejected.
