The mail bomb recovered aboard a cargo jet in England was more powerful than the underwear bomb that failed to detonate on a Christmas flight from the Netherlands to Detroit, the top Republican on the House Homeland Security Committee confirmed to Fox News Saturday.

Rep. Peter King said he had been informed by law enforcement officials that "the quality and the power of the explosive" found in the mail bomb in England is "far more powerful" than the one that Umar Farouk Abdulmutallab had on Christmas Day.

β€œIt shows that this was not a dry run," King said. "They were serious to put together a weapon which is significantly more powerful than the Christmas day bomb."

The two packages were addressed to Jewish groups in Chicago but never made it to the U.S.

Initial tests show the devices contained the same explosive used on the Christmas Day attempt last year – the explosive P-E-T-N.

The one device had a cell phone detonator and the other appeared to be a timer, a source told Fox News. The intelligence tip from the Saudis was very specific and it led to investigators to the tracking numbers of both packages.

King said the plot may be wrapped up based on a briefing by Homeland Secretary Janet Napolitano earlier Saturday.

β€œI spoke to Secretary Napolitano earlier this afternoon, and basically it appears as if, you know, the plot has been stopped, we're not aware of any other activity that's out there," he said. "No one is letting their guard down at all. They are still working on this as if there was an attack coming, but the feeling now is that we believe that this attack has been stopped in all its parts.”

U.S. counterterrorism officials say all signs point to an Al Qaeda plot and the group that was behind the Christmas day bombing "is at the top of the list."

The American cleric, Anwar Awlaki, is now an operational leader of that group - Al Qaeda in Yemen. He is the first American on the CIA's kill or capture list.

Catherine Herridge is an award-winning Chief Intelligence correspondent for FOX News Channel (FNC) based in Washington, D.C. She covers intelligence, the Justice Department and the Department of Homeland Security. Herridge joined FNC in 1996 as a London-based correspondent.