A massive sinkhole has opened up just yards from the fence of a prison - but officials insist there is no chance of any inmates escaping . The hole first appeared just outside the walls of HMP The Mount in Bovingdon , Hertforshire in January . Staff at the 770-capacity prison filled the sinkhole with soil and concrete - but it re-emerged and is now believed to be about 6ft wide and 15ft deep . A massive sinkhole has opened up close to the fence of HMP The Mount Prison - but officials insist there is no chance of any inmates escaping . A 15ft sinkhole has emerged yards from the walls of HMP The Mount Prison in Bovingdon , Hertfordshire . The Mount , operated by Her Majesty 's Prison Service , opened as a young offenders institution in 1987 on the site of a former RAF station . It was immediately fenced off but officials at the category C jail have refused to confirm the exact size and depth . A Ministry of Justice spokesman said : 'We are aware of an issue regarding the land next to HMP The Mount and are working to resolve it . 'There is no risk to members of the public , prisoners or prison staff as the area has been fenced off and is on private property with no public access . 'We are still in discussions with the Homes and Communities Agency regarding future options for the surplus land . 'The Ministry of Justice is required to dispose of any surplus property as quickly as possible while ensuring we get the best value for taxpayers ' money . ' The Ministry of Justice insist there is no chance of inmates escaping - even though the hole has emerged close to the prison . Local resident Ross Butcher , 32 , said : 'All of us had a right laugh about it at the beginning and kept comparing it to the Shawshank Redemption or something . ' I still have n't ruled out the possibility that some prisoners will just pop out of it . It 's only a couple hundred yards from the prison fence . 'There is some concern that more could appear as that land has already been earmarked for a housing development . ' The hole comes after a similar crater opened up in nearby Hemel Hempstead , Hertforshire , last February . It is believed to have been caused by former chalk mines beneath the surface of the ground being exacerbated by the previous winter 's heavy rain . The Mount , operated by Her Majesty 's Prison Service , opened as a young offenders institution in 1987 on the site of a former RAF station . Over the years it changed into a prison for adult males . It is classed as category C meaning it is a closed prison for inmates 'who can not be trusted in open conditions but who are unlikely to try to escape ' .
Sinkhole appeared outside HMP Mount in Bovingdon , Hertfordshire . Hole was filled in with concrete and soil only fot it to re-appear days later . It is just yards from prison walls and believed to be 15ft deep and 6ft wide .