The bomb which exploded outside Liverpool Women’s Hospital contained ball bearings and could have caused “significant injury or death”, counter-terror police have said.

It has also emerged that the bomber, Emad al Swealmeen, spent many months buying ingredients for the device and used a series of aliases.

His brother has been interviewed to gain an “insight” into the 32-year-old’s state of mind.

In an update, officers from Counter Terrorism Police North West said the bomb was made using “homemade explosive” and the ball bearings “attached to it would have acted as shrapnel”.

“Had it detonated in different circumstances we believe it would have caused significant injury or death,” said Assistant Chief Constable Russ Jackson.

How or why the device exploded when it did are still being determined, and officers are “not discounting it being completely unintentional”.

Mr Jackson added: “It is a possibility that the movement of the vehicle or its stopping caused the ignition.”

Detectives are spending “considerable time” trying to understand the approach al Swealmeen used as he purchased the ingredients for his device.

“This is complicated because purchases have spanned many months and al Swealmeen has used many aliases,” Mr Jackson said.

“We are confident, however, that in time we will get a full picture of what purchases were made and how, and if anyone else was involved or knew what al Swealmeen was up to.”

Police spoke to al Swealmeen’s brother on Thursday evening.

The conversation has “given us an insight into (al Swealmeen’s) early years and an understanding of (his) life and his recent state of mind, which is an important line of investigation”, Mr Jackson said.

“We are grateful for members of the public who knew him and have contacted us.”

He continued: “Although there is much scientific work to do on the device to determine what made it up, we have learned a great deal over the past five days.

“We have found no connection between this incident and the terrible events of Manchester in May 2017. The device was also different to the one used in the Manchester Arena attack.”

Al Swealmeen is understood to have arrived in the UK from the Middle East in 2014 and had an application for asylum rejected the following year, but was still in the country.

He is believed to have converted from Islam to Christianity in Liverpool’s Anglican cathedral in 2017.