U.S. department of transportation says to investigate airlines' forceful removal ...

The U.S. Department of Transportation (DOT) said Monday evening that it would probe the incident in which the United Airlines had one of its passengers forcefully removed.

"The DOT remains committed to protecting the rights of consumers and is reviewing the involuntary denied boarding of passenger(s) from United Express flight 3411 to determine whether the airline complied with the oversales rule," it said in a statement.

The response came after a horrific incident took place at Chicago O'hare International Airport on Sunday, when a passenger of Asian descent with bloodied face was literally dragged off a plane by airport police.

United Airlines said that due to oversale of tickets, four passengers need to leave the plane, and when an monetary incentive of 800 U.S. dollars lured no volunteers, flight attendants said they used computers to "randomly" choose four unlucky passengers.

Three passengers complied with the airlines' demand but the fourth, a 59-year-old doctor who said he needed to reach a patient, refused to disembark.

Airport police were then summoned and wrestled the man out of his seat. The man's mouth was hit in the process and bled heavily.

"While it is legal for airlines to involuntarily bump passengers from an oversold flight when there are not enough volunteers, it is the airline's responsibility to determine its own fair boarding priorities," the DOT said in the statement.