Transcript for UK hit by 5th terror attack in last 9 months

George, in a moment but Brian Ross is here with us and, Brian, you have been in touch with your intelligence sources. What are they telling you? British counterintelligence sources, robin, this morning are saying this was a very crude devi, some of the best evidence may be found in the remnants of the bomb but call this bucket bomb a rather crude device, kind of an amateur issue. They didn't use a pressure cooker which is often used by ISIS, that's how they describe further followers what kind of bomb to use but the fact that they have the bomb and remnants will lead to lots of evidence for them, lots of forensic details. Brian, we know that British authorities are treating this as a terrorist attack but has they group claimed responsibility yet? So far, I mean, no claims of responsibility. In Britain there are some 500 active investigations under way right now and some 3,000 people are considered to be on the terror watch list so there are lots of people to look for and there is some concern that the bomber in this case may have been somebody who was injured. They're looking closely at those injured. All of us here at the desk have been talking about the number of attacks in a relatively short amount of time. Exactly. As Ian described all of those on the two bridges and concert in Manchester and an attack on Muslim worshippers, a serious situation and at this point the threat level in Britain remains at severe, one step below critical. We know you'll stay on top of this but let's go back to George

This transcript has been automatically generated and may not be 100% accurate.