Investigators analyzing the deadly crash of Metrojet 9268, the Russian jet that crashed in Egypt, have uncovered intelligence about a “two hour timer.” Though investigators haven’t confirmed the source of the reference, there are two theories: intercepted communications between known terrorist operatives or the existence of physical evidence.

A source not authorized to speak on the record said that based on facts uncovered so far one of the working theories is that a bomb was planted at or near the fuel line or where it attaches to the engine, with the fuel burning off the explosive. This theory would explain the lack of residue immediately found.

“If proven accurate, if ISIS did put a bomb on this aircraft which I believe to be true, it’s a new chapter with respect to ISIS,” said Texas Republican Rep. Mike McCaul.

McCaul, who receives regular classified briefings and cannot discuss specifics, said that the Obama administration has consistently underestimated ISIS by stating that the focus of their march is to gain more territory – not to expand their global reach.

“We always assumed Al Qaeda had this capability but now if ISIS has this capability, the threat to American airlines as well and our homeland, I think is very significant,” said McCaul.

The jet disintergrated approximately 23 minutes into the flight, so investigators are now focused on a “90-minute window” before the flight took off and who had access to the jet. They are interviewing all members of the ground crews, all who had access to the departure lounge, and they are reviewing surveillance images and videos.