Emergency services in County Durham are testing how they would respond to a potential terror attack.
Exercise Butterworth is taking place at the international Riverside Cricket Ground in Chester-le-Street.
It involves a simulated chemical, biological or nuclear attack moments before the start of a match at the Riverside in Chester-le-Street.
The police, ambulance and fire brigade are taking part in what has been described as a realistic scenario.
The aims of the exercise are to test existing joint arrangements, develop the working relationship between them, and encourage further knowledge-sharing.
Stuart Errington, from the County Durham and Darlington Fire and Rescue Service, said: "Let's hope we never have to do this type of event for real, but if we have to we have all of the skills and preparation work already there."