Police have confirmed the explosion on a packed rush hour tube train at Parsons Green underground station, which injured 22 people, was caused by an “improvised explosive device.”

The Metropolitan Police Terrorism Command confirmed they were investigating. Assistant Commissioner Mark Rowley said the IED did not fully detonate.

Rowley said it was understood that “most” of the 22 injured were suffering from “flash burns.”

He added that hundreds of detectives are involved in the investigation, including scouring CCTV footage and speaking to witnesses.

Read more

Domestic intelligence agency MI5 is supporting the police investigation, he said.

Images show a white bucket - seemingly with wires trailing from it - inside what appears to be a Lidl supermarket freezer bag.

Investigators say the device did not fully detonate.

Witnesses have told of an “extremely heavy police presence” and “quite a few people injured” potentially including facial burns. A number of injuries stemmed from a crush of people trying to leave the station.

The incident is being treated as terrorism-related, the Metropolitan Police said.

Armed police are at the station and surrounding homes are being evacuated.

The homemade device is believed to be the same type that was used in the Boston Marathon bombings. Experts believe the device was some kind of crude “pressure cooker bomb” that did not detonate properly.

In April 2013, two such homemade bombs detonated near the finish line of the Boston Marathon killing three people and injuring several hundred more - several of whom lost limbs.

Major General Chip Chapman told Sky News: “It’s no accident this was both in a confined place and a crowded place.

“It seems to be this bomb either malfunctioned or it’s not TATP, the explosives used by groups like ISIS [Islamic State].

Read more

“It’s more like the Boston bomb. It’s almost like a pressure cooker device.”

Major Chris Hunter, who served in Iraq and Afghanistan for more than 18 years, told LBC he was at the COBRA meetings on 7/7 and 21/7. He said the devices then were very similar to the one on the underground on Friday.

Hunter, who is also a former special adviser to the government on counter-terrorism and author of ‘Extreme Risk’ says devices such as these are “very dangerous to move in the early stages.”

Security experts told the Sun the bucket may have malfunctioned on its way to a larger station. Will Geddes told the tabloid: “My feeling is that it’s a premature detonation. I know both Parsons Green and District Line very well. It’s an ideal commuter time.

“It was a premature detonation because it doesn’t sit inside the type of profile that terrorists want for a detonation … Notting Hill or Paddington Station - then you’ve got a much more identifiable location for the world to pick up on.

“The device is really basic. I don’t see a considerable amount of scorched surfaces around the device itself.

“It looks like a firework bucket. I would say it is an ill-conceived device. But there were very significant burns - there was likely to be some kind of toxic element to it.”

The bomb appeared to have been constructed out of flammable materials, a plastic bucket and fairy lights.