Residents in Fleetwood were left startled to see bulldozers on the former Fleetwood Pier site.
There had been complaints that the land was not properly tidied after the pier building burned down in September 2008.
Our officers immediately responded and blocked off access to the cellar
This week Wyre Council, which owns the land but is leasing it to consortium Simmo Developments, explained what was happening at the site.
A spokeswoman said: “On Monday April 10, we received a call stating children had been trying to gain access to the cellar under the Fleetwood pier site.
“Our officers immediately responded and blocked off access to the cellar.
“Following this, our building control officers held a site meeting with Simmo Developments. which surveyed the site and filled in the void.”
Simmo plans to build 15 flats for the over 55s on the site but there are now more than 600 objections to the scheme, which is similar to one rejected by planners in January.