SEVEN people are being treated at the scene of a major incident in Henley town centre.
Emergency services are dealing with the suspected gas or chemical leak at WH Smith in Bell Street.
Casualties are being checked over by paramedics at the roadside and in ambulances.
Staff from WH Smith were outside the store covering their months with their eyes streaming.
Bell Street is closed from the junction of Hart Street to beyond the Waitrose exit.
All the shops on both sides of the road between the two points have been evacuated.
Duke Street is only accessible to pedestrians and crowds have gathered at the ends of the cordon.
Firefighters and police were called at about 2.35pm.
Jill Buckett, who works in Robert Dyas in Bell Street, said: “The girls came out with their eyes streaming and they were coughing and said ‘something’s happening inside’.”
Lisa Allen, who works in White Stuff also in Bell Street, said: “I noticed three women rush out.
“The manager explained there was some kind of fumes or chemicals and said they had to get everybody out.”
The cause of the leak is not yet known.
Chief inspector Graham Walton, of Thames Valley Police, said: “We had reports of customers leaving the premises and something had gone off.
“We don’t know what it is but certainly it’s not terrorism- related.”
There are currently three fire engines and three ambulances at the scene as well as a special operations unit in Kings Road car park.