President Barack Obama spoke about Thursday's Malaysia Airlines crash, calling the deaths of the 298 passengers "an outrage of unspeakable proportions" and saying "we know at least one American citizen" was killed.

Obama named Quinn Lucas Schansman as the victim from the U.S.

Obama also called for an immediate ceasefire in Ukraine.

"This was a global tragedy. An Asian airliner was destroyed in European skies, filled with citizens from many countries, so there has to be a credible international investigation into what happened," Obama said in a statement delivered from the White House Friday.

"Russia, pro-Russian separatists and Ukraine must adhere to an immediate cease-fire. Evidence must not be tampered with," Obama continued.

"It’s time for peace and security to be restored in Ukraine," Obama said.

Obama repeated sentiments shared by U.S. officials, saying it's believed a surface-to-air missile from an area controlled by pro-Russian separatists took down the jet.

Obama had briefly addressed the plane crash during an appearance in Delaware on Thursday, saying the United States "will offer any assistance we can to determine what happened and why."

Vice President Joe Biden also addressed the plane crash during a Thursday appearance at the 2014 Netroots Nation conference, saying the incident was "not an accident."

Below, more from the AP:

U.S. officials have said the plane was shot down Thursday by a missile. But the Obama administration has not said who it believes is responsible for firing the missile.

So far there has been no confirmation of any Americans on board the Malaysia Airlines plane that was carrying 298 people.

The plane was shot down near the border between Ukraine and Russia. The incident occurred one day after Obama announced broader economic sanctions against Russia for its threatening moves in Ukraine.