One person remains in hospital and two others were also injured after a hole appeared in the stand at last night's T20 cricket match in County Durham.
The incident happened during the sell-out match between England and the West Indies at the Emirates Riverside Ground in Chester-le-Street.
The North East Ambulance Service said it responded to a 999 call and treated one of the causalities, who was left seriously injured.
They were taken to Newcastle's Royal Victoria Infirmary for further treatment.
A spokesman for the hospital confirmed the individual was still being treated this morning for "non life-threatening injuries."
The two others left hurt were treated by medical cover brought in for the event by its organisers.
Pictures on social media showed part of the floor of the North East Stand had collapsed as fans watched the international game.
Twitter user @ChristianCeriso posted an image of two stewards standing guard either side of what appeared to be an opening directly beneath a seat.
Fans from the entire seating block were ushered away from the area by stewards and guided to other parts of the ground to watch the remainder of England's 21-run defeat.
Durham County Cricket Club later confirmed the three spectators were injured during the course of the second inning after falling on unstable flooring in the North East Terrace.
The stand was said to have passed inspections in the week before the match.
Durham have begun the process of collecting witness statements from stewards and first responders.
A club statement 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."
Windies captain Carlos Brathwaite said after the match that some of his players felt conditions on the pitch were "unsafe" and was prepared to take an abandonment after wicketkeeper
Chadwick Walton slipped while fielding, needing lengthy treatment.
A Durham Constabulary spokesman said: "Durham Police supported stewards with an orderly evacuation of spectators from one of the stands when a section of the floor became unstable.
"We want to thank everyone for their support in this."
Armed police were also in attendance at the ground, with Durham Constabulary telling people in advance of game that there would be enhanced security checks.