Terror threat level 'critical' after ISIS claims attack in UK Tube

LONDON (WLS) -- One thousand heavily armed British soldiers and additional police were deployed to London streets late Friday after a suspected ISIS bomb blew up on a packed rush hour train.

"Like a fireball, a fire blast, that just went up quickly and as soon as it went up people left" said eyewitness Luke Walmsley. The blast occurred in the sixth car of a seven car train that had a capacity of more than one thousand people.

UK Prime Minister Theresa May increased the nation's terror threat to its highest level, "critical," which means another attack is expected immediately.

A wide net was being cast by law enforcement after the 8:20 a.m. subway blast that injured about two dozen people, most by what authorities called "flash burns." The wounded include a young boy, believed to be about 10 years old. There was a single bomb found but the number of suspects being sought on Friday night was not known.

Investigators from Britain's MI5 counter-terror unit, now assisting the investigation, say that the improvised explosive device (IED) used on a train pulling into the Parsons Green station in west London was not intended to be a suicide attack. The homemade device was found inside a utility bucket made of plastic. The bucket was inside a plastic grocery store bag. Wires could be seen protruding from the device. The IED was attached to a crude timer according to police sources and had Christmas lights intertwined with the wiring. The bomb contained nails that become shrapnel during a blast.

Investigative sources consider it "likely" that the bomb contained an explosive known as TATP. That chemical, the explosive of choice for ISIS and al Qaeda terrorists, is known as the "mother of Satan" because of its potency.

Had the device fully detonated, authorities believe that the damage and injury would have been much more severe. Anti-terror police are operating under the theory that it may have accidentally gone off early-prior to arriving at the Westminster Tube station.

"It was just this sheet of orange flame and this huge bang and obviously everyone ran off" said eyewitness commuter Izzy Price. Another passenger, Natalia Diaz said that "people were just getting crushed and we were just trampling each other. It was just every man for themselves." Investigators suspect the suspect, and any accomplices, managed to escape during the stampede of survivors.

Counter terrorism detectives from Scotland Yard have been looking at CCTV footage on the train and at stations and examining subway payments records to identify those responsible.

The al-Qaida magazine "Inspire" has recently urged jihadist devotees to target trains and public transportation. As the I-Team first reported in October 2010, al-Qaeda has been using its online propaganda to recruit and instruct potential "lone wolf" bombers.

Friday's attack was the fifth terrorist strike in the UK in six months and prompted a tweet from President Donald Trump stating that it was carried out "by a loser terrorist," and that "these are sick and demented people who were in the sights of Scotland Yard."

The suggestion that British investigators knew of the terrorist in Friday's incident drew criticism from Prime Minister May. "I never think it's helpful for anybody to speculate on what is an ongoing investigation" she said.

London's mayor Sadiq Khan said that he "utterly condemns the hideous individuals who attempt to use terror to harm us and destroy our way of life" and pledged "those responsible will be caught."

Britain's top law enforcement officials said late Friday said that they were making progress in identifying and arresting the bombing suspects.