The incident happened on Sunday evening, when the gang managed to get into the Grade II-listed building. JD Wetherspoon has recently pulled out of plans to open a pub at the site.
And on Monday, officers were called out again, this time after people on a ghost hunt attempted to get into a stable building in Chillingham Castle.
In both cases, advice was given to the landowners and no offences were committed, police have said.
However, the incidents have prompted police to remind people not to fall foul of the law this Hallowe’en by going onto private land without permission and not to put themselves in danger.
Neighbourhood Inspector Liz Hall said: “We don’t want to stop people having fun this Hallowe’en, but we do want to make people aware that they must get permission from the landowner before entering buildings or land.
“If they don’t, then they are committing trespass and any damage caused would be treated as criminal damage and they could find themselves being arrested and brought before the courts.
“We also want to keep people safe, and an old empty building which may seem fair game for a ghost hunt, may actually be rather dangerous. If you go inside an empty building you’re also putting yourself at risk as some buildings may be in a poor state of repair and you could be injured.
“We want to encourage people to enjoy Hallowe’en safely by attending an organised event or party, not by putting themselves in actual danger.”