The travellers were spotted entering land at Philpott's Farm just of High Street on Wednesday evening (July 13) and there have been police and security spotted on the site.
Police have said that no arrests have been made in connection with the travellers and no criminal offences have been disclosed.
“Before police can make a direction to leave part of the legislation requires the landowner to take steps to ask for the trespassers to leave and vehicles to be removed.
“ Hillingdon borough officers have spoken to the relevant landowners accordingly.”
A van of security dogs was spotted at the entrance to the green space on Friday morning (July 15) and there have been reports of rubbish dumped in the fields.
getwestlondon has approached Hillingdon Council for comment.