A group of travellers have set up camp on a council-owned playing field in Gloucester.
Twenty caravans were moved onto the site at Plock Court on Tuesday evening.
A Gloucester City Council spokesman said that when council staff arrived they found a new security gate and lock had been forced open.
He added: "Officers are making sure no-one else can move onto the land and we are working with our legal team to find a way of having the group evicted."
Last August another group of travellers were moved on from the site after they were served with a court order.