U.S. officials have confirmed to several media outlets that the Malaysia Airlines passenger plane that crashed near the Ukraine-Russia border Thursday was shot down by a surface-to-air missile.

The origin of the missile remained unclear, and both government officials and pro-Russia separatists fighting in the region denied responsibility.

There were 298 people on board, 283 passengers, including 3 infants, and 15 crew members. Ukrainian authorities told U.S. Embassy officials that everyone on the plane was "believed dead" and that the aircraft debris was scattered over a 10-mile swath of land, ABC News reported.

Malaysia Airlines posted a list of passenger nationalities on its website for the 298 passengers and crew: 154 Dutch, 27 Australian, 43 Malaysian (including 15 crew and two infants), 12 Indonesian (including one infant), 9 British, 4 German, 4 Belgian, 3 Filipino and one Canadian. The airline said it did not yet know the nationalities of the remaining 41 passengers.

An aide to Ukraine's interior minister quoted by Interfax claimed the total number of dead in the crash was more than 300 and included 23 U.S. citizens.

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President Barack Obama said the White House was working to determine whether there were U.S. citizens aboard the plane.

Speaking at a conference in Detroit, Vice President Joe Biden also commented on the crash, saying the aircraft "apparently had been shot down. Shot down. Not an accident. Blown out of the sky.

“We have seen reports that there may have been American citizens on board, and obviously, that’s our first concern," he said. "We’re now working every minute to confirm those reports as I speak. This is truly a grave situation.”

In an interview with Charlie Rose, former Secretary of State Hillary Clinton said, "there does seems to be some growing awareness that it had to be Russian insurgents. How we determine that will require some forensics. But then, if there is evidence pointing in that direction, the equipment had to come from Russia."

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Clinton said if there is evidence linking Russia to the attack, "that should inspire the Europeans to do much more" to support Ukraine.

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Meanwhile, the head of Ukraine's emergency services told Reuters that search efforts at the scene of the crash were being hampered by "armed terrorists."

Anton Gerashenko, an adviser to Ukraine's interior minister, wrote on Facebook soon after the crash that the plane was flying at an altitude of 33,000 feet when it was hit by a missile fired from a Buk launcher.

Separatist leader Andrei Purgin told the AP that he believed Ukrainian troops had shot the plane down, but did not say why he was certain. Witnesses quoted by Russian media outlets said they saw a plane being hit by what they thought was a rocket, according to the news service.

Ukrainian President Petro Poroshenko said Ukraine's military was not responsible for the reported attack, which he called an “act of terror."

"We do not exclude that this plane was shot down, and we stress that the Armed Forces of Ukraine did not take action against any airborne targets," Poroshenko said. "We are sure that those who are guilty in this tragedy will be held responsible."

Malaysia Airlines earlier tweeted that it had lost contact with Flight MH17 over Ukrainian airspace:







Malaysia Airlines has lost contact of MH17 from Amsterdam. The last known position was over Ukrainian airspace. More details to follow. — Malaysia Airlines (@MAS) July 17, 2014



The airline later confirmed the crash, approximately 25 miles from the Russia-Ukraine border:









Flight MH17 operated on a Boeing 777 departed Amsterdam at 12.15pm (Amsterdam local time) and was estimated to arrive at Kuala Lumpur International Airport at 6.10 am (Malaysia local time) the next day. The flight was carrying 280 passengers and 15 crew onboard.



The plane crashed near a village called Hrabov in the Donetsk region, an area that has seen clashes between Ukrainian forces and pro-Russia separatist rebels in recent days.



On Wednesday evening, a Ukrainian fighter jet was shot down by a Russian plane, Ukrainian authorities told the AP.

Prior to Thursday's crash, the U.S. Federal Aviation Administration, along with several other countries, had warned pilots not to fly over parts of Ukraine.

White House spokesman Josh Earnest said Obama directed his national security team to be "in close touch" with Ukrainian authorities.









Earlier Thursday, Obama spoke by phone with Russian President Vladimir Putin, at Moscow’s request, to discuss new sanctions announced by the United States and European Union. According to the White House, Obama first learned of the crash during the talk with Putin.



Video uploaded to social media shows debris falling from the sky near the crash site.









This is the second tragedy to hit Malaysia Airlines in recent months. The Ukraine crash comes just four months after Malaysia Airlines Flight M370 lost contact less than an hour after takeoff from Kuala Lumpur International Airport and vanished. That flight was carrying 227 passengers and 12 crew members.



With Olivier Knox reporting from Washington.