A race had to be stopped dramatically because the starting boxes could not be removed from the track.
It became clear there was a problem when officials tried to mark the field around the home bend in Chelmsford on Saturday.
Nine runners and riders were traveling at speeds of more than 55 km/h, but had to stop abruptly to avoid the stalls, which were still on the track at the entrance to the home straight.
All horses and jockeys were unharmed and the race was declared void.
Jane Chapple-Hyam, who trained runner Salamanca, told the Racing Post: “When they load horses into the stables they turn the tractor off and I believe if the horses jumped out the tractor wouldn’t go into gear so they couldn’t switch. get it off the track.
“They didn’t have enough time to send the flagmen to the straight. It was quite scary.”
Jockey Alistair Rawlinson, who was on board Penzance, said all riders involved deserved credit for pulling away safely and avoiding accidents.
“We were second so we were one of the first to arrive on the scene – it could have been a disaster,” he said.
“The boys showed a lot of horsemanship to stop in a short time when we are about to hit top gear.”
A statement from the racecourse said: “The safety of our participants is and will always be our top priority.
“We are deeply relieved that no harm was caused to the jockeys, horses or staff involved. Tonight’s incident is unprecedented in the 10 years of Chelmsford racing and although the racecourse was not directly responsible for what happened, we fully acknowledge our role as the racecourse hosting the race.
“We are committed to working with the British Horseracing Authority (BHA) and our partners to conduct a thorough investigation and ensure events like this do not happen again.
“Refunds will be arranged for the affected connections and they will be contacted with further information.”
A report from the stewards said: “An investigation was launched into the deployment of the stop flag in the closing stages of this race as the boxes could not be removed from the course.
Present at the inquest were the director of racing, the race secretary and the course trainee, both starters, jockeys Billy Loughnane and Harry Davies, the stables team leader and the tractor driver.
“As all runners had retired and the judges were unable to determine a result, the race was declared void and a report forwarded to BHA headquarters.”