The International Olympic Committee tells TMZ Sports ... they are officially investigating Egyptian judo fighter Islam El Shehaby to find out why he refused to shake the hand of his Israeli opponent.
"The IOC has set up a Disciplinary Commission to look into this matter," a rep for the IOC tells us.
As we previously reported, Israeli fighter Or Sasson defeated El Shehaby in a 100kg judo match in Rio on Friday -- and in customary judo fashion, extended his hand for a handshake.
El Shehaby refused ... though when the ref called both men back to the mat, the Egyptian gave a quick head bow.
There are reports that El Shehaby's refusal was politically motivated under pressure from powerful Egyptians who did not want to see him be cordial with an Israeli.