Health and safety inspectors have taken over a probe into the cause of a horse-bolt incident in which a woman died.

Terrified visitors screamed and fled as the animal charged at the Nowton Park Country Fair in Bury St Edmunds at around 4.30pm yesterday.

One of those injured - a 57-year-old woman from Bury - died of her injuries this morning. She has been named as Carole Bullett.

An investigation into the cause of the tragedy has been launched and police have today transferred lead responsibility to the Heath and Safety Executive (HSE).

A spokesman for the HSE said the organisation's staff were no longer at the scene of the incident and said it was investigating because it invoolved a local authority event on local authority land.

A police spokeswoman said: 'The HSE are the lead agency now. 'We have carried out our responsibilities in terms of managing the incident as it happened, now it is for the HSE to investigate the circumstances and see if any action needs to be taken.

'We will assist the HSE by passing everything we have gathered thus far to them.'

Mystery still surrounds what caused the horse - understood to be called Lucas - to bolt.

Lucas, a four-year-old Breton horse, was set to be sold for meat at a market in Duras when he was rescued last September. Lucas was bought by Duncan Drye, owner of the Carriage Tours of Bury St Edmunds.

After months of care, attention and special training, Lucas joined a team of horses pulling visitors in carriage tours around the historic sights of Bury St Edmunds.

Mr Drye was this morning unavailable for comment.

One of those injured in the incident, Cindy Taylor, 65, was knocked to the floor when her mobility scooter was crushed by the horse, which – along with its carriage – careered through busy crowds at the popular event.

'It was horrendous. Just terrible,' Mrs Taylor, of Bury, said: 'I was terrified when I saw this horse coming towards me. Something had certainly spooked him.'

The animal, which had earlier been giving carriage rides to visitors at the fair, reportedly broke free from where it was tethered in the avenue of lime trees at the site, running over several people.

A BMX display had been going on at the time and it is believed many people had their backs to the horse as it approached.

Ruth Mills, 18, from Bury, was watching the entertainment in the main arena with her boyfriend, Jamie Langley, 21, when the horse charged towards them.

'I just remember a lot of screaming and shouting,' she said. 'As I turned around the horse was just behind me. My boyfriend hadn't got out of the way quickly enough and the horse got him in the back.'

Andy Bowes, from Sudbury, was part of a crowd of people watching the BMX bike stunt display when the runaway horse ploughed into several people, throwing one person 'eight feet in the air'.

Mr Bowes said: 'I was standing watching the bikes and heard somebody shout 'oh my God, there's a horse' and it was literally 10ft away from me. I managed to throw myself out of the way and as I did I saw it plough straight into the crowd.

'It was horrendous. I don't know what happened, something obviously spooked the horse. The guy standing next to me got knocked 8ft into the air.'

He described how the horse came to a stop and lay down, appearing to lay on top of a person as people tried to make the animal move

He praised the quick response of the St John Ambulance staff who were on the scene within seconds.

Tony Curd, St John Ambulance County Commander, said: 'Our volunteers were providing medical cover at the event with an ambulance and mobile treatment centre and were able to respond immediately.

'They dealt with multiple casualties under difficult circumstances and are to be commended for their prompt actions. Our thoughts are with those injured this afternoon, at what should have been an enjoyable Father's Day event.'

Any witnesses are being asked to call Suffolk Police on 01473 613500.