An investigation has begun after a wall and scaffolding collapsed at a demolition site in Bradford city centre.

Part of a wall at the site of the former Thompson Mill, in Tetley Street, which was largely destroyed by fire last October, collapsed on Tuesday, bringing down scaffolding along with it.

A Health and Safety Executive spokesman yesterday confirmed an investigation into the collapse had begun as demolition workers from Thomas Crompton tried to make the site secure yesterday afternoon and clear the blocked road.

HSE inspector Paul Yeadon, who was at the site yesterday, told the Telegraph & Argus: “At the moment they are going through the process of making it safe so the road can be re-opened when possible – we hope that will be today, possibly tomorrow.”

John Ferguson, 28, of Hightown, Cleckheaton, was leaving work on Tuesday evening when he heard the scaffolding beginning to creak.

He said: “I looked over and turned just in time to see the scaffolding and what I thought was the wall come down crashing on to the road.

“One of the windows is smashed – there are some flats next to it and it looks like some damage has been caused to one of them.

“I’ve never heard anything like it before – it just completely crashed down, there was a loud crashing noise.”

Emergency services were called to the site at about 6.30pm on Tuesday after the wall and scaffolding came down.

Mark Rogerson, watch commander at Bradford fire station, said crews used thermal imaging cameras and a sniffer dog to make sure there was nobody trapped under the rubble.

He said: “The building itself is down, but they left up the external walls which go around the outside of the site and around the outside of that was the scaffolding which they had been using.”

Mr Rogerson said it was not yet known what caused the 20ft by 40ft section of the wall to collapse.

A West Yorkshire Police spokesman said a nearby window was smashed by a piece of the scaffolding, which was about three stories high.