Deputy National Security Adviser Tony Blinken said Sunday that it's too early to say what caused a flight en route from Malaysia to China to go missing.
"It is too soon to tell what happened, why it happened," Blinken said on CNN's "State of the Union."
Reports that two passengers on the Malaysia Airlines flight, which went missing Saturday, apparently traveled together with stolen passports "raise questions and concerns," said Blinken. But he added that it's too early to draw conclusions.
Blinken said the U.S. has dispatched the FBI and other experts to help with the investigation.
House Intelligence Committee Chairman Mike Rogers (R-Mich.) said on ABC's "This Week With George Stephanopoulos" that the investigation is "certainly in its early stages. He added, "It's not common but its not unheard of either that stolen passports can be repurposed and used."