THIS article was last updated at 3.40pm.

TOXIC fumes have left seven people requiring treatment by paramedics and also caused roads to be closed around High Wycombe town centre this morning.

Fire crews and police have been on the scene after a 'chemical incident' involving workmen.

Buckinghamshire Fire and Rescue said this afternoon it had been caused by a chemical reaction in a road tanker at the Pann Mill Water Works in Abbey Way.

Roads were shut including London Road from Gordon Road onto Abbey Way.

The A40 on the junction of Gordon Road was closed, as well as Easton Street and Queen Victoria Road at the roundabout close to the police station.

The streets re-opened just after 2.30pm this afternoon.

A call was made to Thames Valley Police at 9.42am from High Wycombe Irish Association about a “nasty toxic smell” apparently emanating from the Abbey Way area.

It is not currently clear as to exactly where the incident happened, police said.

Experts from the Health and Safety Executive are on the way to assess and investigate the incident.

Police spokesman Chris Kearney told the Bucks Free Press: “It looks like workmen who are down there, who are doing some kind of chemical clean up, have mixed two substances together which has reacted and it's started kicking out toxic fumes.

“Fire crews have gone to the scene to cordon off the area to protect members of the public.

"The scene has been cleared.”

Seven people have been treated by paramedics but it is not thought at the moment they are in serious condition.

However, they will be checked out in hospital to ensure they have suffered no adverse affects from the inhalation of toxic fumes.

Lawrence Jackson, 20, a student from High Wycombe saw “a large cloud of thick white smoke” after turning on to the London Road just after 9.35am.

“I thought it was dust at first as I saw a couple of workers strolling out, but then I couldn't breathe it in and it stung my throat and eyes.

“At first it smelled like sewage.”

Having seen gardeners close by with weeds he wondered if the river was being dredged.

“But then it got really sharp and smelled like really strong sulphur,” Mr Jackson said. “I sort of held my breath walking through it after that, even though the breath I was holding was filled with the fumes.

“It wasn't until I got around the corner by the courts that i could breathe properly again which was when I started coughing.”

He only realised it was a more serious incident after seeing the emergency services on his trip home.

He said he has not felt right since after breathing the fumes.

The Health and Safety Executive will now speak to the firm involved and look into what has happened and why.