Durham County Cricket Club says spectators fell when the floor became unstable - but their injuries are not thought to be serious.
The incident took place midway through England's innings on Saturday night, when a section of flooring appeared to give way at the Chester-le-Street ground.
Pictures show stewards standing around a square-shaped hole in one of the stands.
A statement from Durham County Cricket Club read: "During the course of the second innings between England v West Indies at Emirates Riverside, three spectators were injured when a small section of the North-East Terrace flooring became unstable causing them to fall.
"Stewards took precautionary action and evacuated that area of the stand efficiently. The stand is a permanent fixture at the venue and had passed inspections in the week prior to the match."