EgyptAir: US Satellites Show No Indications of Explosion Along Flight Path

— -- U.S. officials say that government satellites show no indications of an explosion along the flight path of the missing EgyptAir flight.

The officials are looking into whether a terrorist act brought down Egypt Air Flight 804, but are facing a frustrating reality: few known facts.

A review of imagery from U.S. government satellites has so far produced no heat signature or indication of an explosion along the plane’s flight path, officials said. U.S. officials now want to review the satellite images taken by other nations and private companies to see if they might offer a better view.

Nevertheless, some U.S. officials wonder whether the plane’s reported turns and apparent rapid descent suggest an explosion brought it down.

“It doesn’t look good,” one official said, noting the lack of a mayday call and no known mechanical issues with the plane.

But “we don’t have any forensic evidence from the plane yet,” another official said. And without forensic evidence, it’s just “too early to tell” what happened, according to a third official.

The possibility of pilot suicide or another deliberate act by a pilot must also be considered, sources said.

Meanwhile, the U.S. government is undertaking an intensive background investigation of the pilots and crew, and the names of passengers on the manifest are being run against all U.S. and western terror watch-lists, officials said.

The U.S. government is also trying to obtain information about who had access to the plane during its stops in other countries -– particularly Tunis, Tunisia, and Asmara, Eritrea –- over the 48 hours before the plane disappeared, the officials added.

U.S. intelligence agencies are also poring over information to see if radicals using known channels and websites have been boasting about the attack.

So far no credible claims of responsibility have been received.

ABC News' Mike Levine contributed to this report.