Feds conducted series of tests to determine credibility of new aviation threat

— -- U.S. authorities became convinced that security measures for certain U.S.-bound flights needed to be boosted only after conducting a series of tests to determine the credibility of new intelligence, ABC News has learned.

Earlier this year, authorities obtained intelligence indicating that ISIS associates were trying to develop explosives-laden electronics that could be smuggled aboard planes, according to sources familiar with the intelligence.

The subsequent tests were executed in recent weeks, looking to determine whether terrorists could carry out the latest form of attack with a bomb hidden in electronics.

The tests led authorities to one conclusion: "It can be done," one source told ABC News.

The Department of Homeland Security ultimately banned all electronics bigger than a cellphone from the cabins of some direct flights to the United States from 10 airports in eight Muslim-majority countries.

Sources said that the airports affected by the restrictions were not directly named in the most recent threat intelligence gathered by authorities, but those airports were identified through intelligence analysis paired with other government information.

In an interview with ABC News, Rep. Eric Swalwell, D-Calif., a member of the House Intelligence Committee, warned about the "new aviation threat."

"We know that our adversaries, terrorist groups in the United States and outside the United States, seek to bring down a U.S.-bound airliner. That’s one of their highest value targets. And we’re doing everything we can right now to prevent that from happening," Swalwell said Tuesday.

Nearly two years ago, ABC News first reported that an internal investigation of the Transportation Security Administration revealed security failures at dozens of major U.S. airports. Undercover investigators were able to smuggle mock explosives or banned weapons through checkpoints in 95 percent of trials. The series of tests were conducted by Homeland Security Red Teams who posed as passengers.