Updated

Threat levels in the U.S. are “extremely high,” as intelligence indicates the Islamic State group and other terror groups are using small-scale plots to build toward another 9/11-style attack, acting Department of Homeland Security Secretary Elaine Duke warned.

“The terrorist organizations, be it ISIS or others, want to have the big explosion like they did on 9/11,” Duke said Tuesday, speaking at the U.S. Embassy in London, Britain's Express reported. “They want to take down aircraft. The intelligence is clear on that.”

Their ultimate goal is “creating terror,” and a van attack in London, as well as sporadic knife attacks, accomplish just that, while never giving up on a “major aviation plot,” Duke added.

Duke became acting head of DHS in July, when Gen. John Kelly left the position to become White House chief of staff. President Donald Trump recently nominated Kirstjen Nielsen to lead DHS, but the appointment awaits U.S. Senate confirmation.

On Tuesday, Duke underscored the importance of tightening security around the world, with laptops posing one of many threats to airline industry.

She also called upon technology leaders to help combat ISIS propaganda spread on the Internet, as home-grown terrorists have increased in the United States.

‘Terrorists are strong, they are adaptable and the terrorist threat is the highest it has been since pre-9/11. We have got to have every tool that’s possible,’ she added.

Click here to read more from the Express.