A groundsman’s mower fell into a 45ft deep hole leading into a 19th Century mine shaft as he rode over it while carrying out maintenance work in a Bradford park.
The groundsman was uninjured.
The hole appeared in a football field in Harold Park, Low Moor, on Tuesday afternoon.
When the mower was pulled out, the 45ft deep and 9ft wide hole was revealed.
The hole has since been fenced off and security put in place to prevent the public getting near it while the Coal Authority look to fill it.
Councillor Val Slater (Lab, Royds) said the Council’s contractors were carrying out the work when the hole was discovered.
She said: “The vehicle they were using, a little ride-on tractor or mower, went into the hole. He was OK.
“I think when they got the vehicle out they discovered that it was quite a substantial hole.
“It is worrying because it was a potential hazard and to some extent it’s fortunate that it was a piece of machinery that triggered it and not a person.
“There was very little that the Council could have done because we were unaware that it was there.
“It wasn’t actually on any of our maps. I understand that the shaft dates from about 1850 and subsequently it has been discovered on some old maps that the Coal Authority hold, but it certainly wasn’t on any maps that the council has.”
Coun Slater said the Council’s emergency planning department will be looking into whether any other holes could appear in the area.
She said: “I’m sure the Coal Authority, having discovered this map, will be taking all necessary steps including identifying any other hazards in the area and dealing with them before any other unfortunate accident occurs.”
John Delaney, the Coal Authority’s corporate services manager, said it was informed of a collapse at about 3.30pm on Tuesday.
He said: “The Council had erected some fencing around it.
“We installed additional fencing – obviously public safety being paramount.
“The collapse is a collapse of a known coal mine shaft.”
Mr Delaney said the authority, along with contractors Mines Rescue Services, secured the site and had employed a nightwatchman to continue public safety at the site.
He said: “We will fill it in with stone. We are in the process if getting a contractor in and necessary materials to enable this work to commence.
“We hope it is done as quickly as we can – obviously this is a park and it needs to be done.”
Ian Bairstow, the Council’s strategic director for environment and sport, said: “Emergency planning and other staff attended the scene to investigate with our partners in the emergency services to ensure the safety of the public is not put at risk and to investigate ways to close up the shaft and repair any damage caused to the park.
“We will continue to monitor the situation and carry out tests to ascertain whether further subsidence is likely to occur in the future.”