Seoul and Washington's joint probe is now under way to determine what caused the crash of a South Korean passenger plane in the U.S. on Saturday.
 
Seoul's Ministry of Land, Infrastructure and Transport said an investigator and an Asiana Airlines official joined the probe at the headquarters of the U.S. National Transportation Safety Board in Washington early Wednesday morning, Korea time. 
 
With their U.S. counterparts, they will analyze the black box of Asiana Airlines Flight 214, a Boeing 777, which crash-landed at San Francisco International Airport. 
 
On Tuesday, South Korean and U.S. investigators interviewed the two other pilots that were aboard the plane to confirm how the plane was being flown just before it crashed. 
 
The investigators are also probing San Francisco International Airport’s air traffic controllers to determine whether there were any problems with the control system.