A Portland, Ore.-bound flight made a "level two emergency" stop in Chicago Tuesday night after passengers said three men, reportedly of Middle Eastern descent, were acting strangely, even fighting with flight crews.

At least one of the men walked back to the area of the plane where flight attendants work, laid down and began complaining of illness. That man engaged in "some sort of altercation" with the flight attendant, a passenger said.

At one point another man, who was pacing back and forth in the aisles, also got into a "verbal altercation" with a flight attendant, according to a passenger.