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By John Dodge

CHICAGO (CBS) — A Malaysian Airlines passenger airplane has crashed in southeastern Ukraine, with nearly 300 souls on board.

That is one fact that is known about the tragedy. We also know that the flight originated in Amsterdam and was flying to Kuala Lumpur, the capital of Malaysia.

Additionally, the area has been the scene of fighting between separatist rebels who want to break away from Ukraine and align with its neighbor, Russia.

What we don’t know is how the crash happened, or who may be responsible.

Reports that the plane was shot down by a ground-to-air missile might be a logical leap of speculation, given the fighting in the region.

However, there is no official confirmation at this point (4 p.m. Chicago time) to support that.

Several media outlets are reporting, attributed to a Facebook post from an adviser to Ukraine’s Interior Minister, that the plane was shot down.

Shortly after 3 p.m. Chicago time an online message, purportedly from a top pro-Russian rebel leader in Ukraine, claimed responsibility. However, that post was quickly taken offline and it’s veracity could not be determined.

In the posting, Igor Girkin wrote, “We warned you not to fly in our skies.” However, the message also refers to military aircraft, not a passenger plane.

There is no official confirmation from anybody else in Ukraine’s government, the U.S. government, the Russian government or Malaysian Airlines.

Later Thursday afternoon, CBS News Correspondent David Martin reported that U.S. intelligence determined the plane was shot down by a missile. However, it was not known from where the missile was fired or who may be responsible.

Then Russian President Vladimir Putin placed the blame on Ukraine’s government.

Ukraine’s president, Petro O. Poroshenko, said he was calling for an immediate investigation of the crash of the plane.

In brief remarks on Thursday afternoon, President Obama vowed to offer any assistance needed to help investigate the tragedy. He said his priority is to help determine if any U.S. citizens were onboard.

We also know, based on multiple reports, that the plane was flying at 33,000 feet before it disappeared from radar.

AP reports that the crew did not make a distress call.

Images posted on Twitter show a ghastly scene.

Journalists in the area from the Associated Press and Reuters have reported burning wreckage and several bodies on the ground.

Reuters is reporting that there were 23 U.S. citizens onboard the flight, but it was not immediately known if any were from Chicago.

The exact number of the dead also isn’t known yet.

There are other unanswered question that might take a long time to resolve, including why a passenger airliner was flying over a hostile area of a country in which both sides were known to have anti-aircraft missiles.

The precise capabilities of those systems are not fully known, either.

CBS News reports: The Malaysia Airlines plane is a Boeing 777-200ER, which was delivered to Malaysia Airlines on July 30, 1997, according to Flightglobal’s Ascend Online Fleets, which sells and tracks information about aircraft. It has more than 43,000 hours of flight time and 6,950 takeoffs and landings.

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