The owners of the site where Ana Kriegel was murdered were told by a local authority it was being trespassed on and might end up being used by rough sleepers.
Fingal County Council raised security issues over Glenwood House in Lucan, Co Dublin.
The 14-year-old girl was killed at the site, which now has planning permission for a care home, in May 2018.
Officials were concerned it would be used in the run-up to Halloween to find material for bonfires.
In correspondence with the owners’ representatives last month, the local authority said they had carried out an inspection and discovered a damaged fence at Clonee Road.
One email said: “The site can now be accessed by pulling this fence aside.
“There appeared to be signs of trespass also within the site.”
The council also warned of other access points including a back entrance to the farmyard. An email said: “Consideration should be made to close up the doorways to these outhouses as they could provide a shelter for people sleeping rough.”
A temporary metal roof had been installed to make the shell of the building “weather tight”.
Openings to the front and rear had been blocked up to prevent access.
Two openings to the building had also been braced. However, an inspection found one of them had already “been interfered with”.
The developers said the additional works would be carried out.
