Security measures at the former Toys R Us site could be ramped up after people entered the vacant building.
Leaseholders have warned against going in the stripped-out unit for health and safety reasons and the risk of prosecution.
Footage posted on social media showed people ‘urban exploring’ inside the derelict building near Southampton Central Railway Station.
This comes as work continues behind the scenes on proposals to redevelop the key city centre site.
WBS Growth Partnership LLP, a joint venture between Aviva Capital Partners, Southampton City Council and the University of Southampton, acquired the leasehold for the council-owned plot early this year.
A spokesperson for WBS Growth Partnership LLP said: “Since taking control of the site, we have sought to tidy up the site and enhance the current car parking arrangements, so that we have an increased customer presence in and around the site.
“We are aware of the footage shared on social media and have shared this with our security contractor to facilitate a review of building security resulting in additional measures being taken.
“Members of the public are urged not to enter any vacant, secured buildings due to the potential health and safety risks and the risk of prosecution.”
Footage inside the building has been posted on social media in recent weeks, including by TikTok accounts @urbex.brennan and @nm.0980.
WBS Growth Partnership LLP, which is understood to have a 250-year lease, is looking to find meanwhile uses for the 4.6-acre site or consider demolition this year while work progresses on redevelopment proposals.
The long-term plan is to deliver a new mixed neighbourhood with a focus on innovation, enterprise and education alongside offices and residential uses.
Stories were appointed development manager for the project.
Since Toy R Us closed in 2018, the building has been empty except for a period when it was used to store donations for Ukrainian refugees.
Former leaseholder Packaged Living secured planning approval for a scheme featuring 603 flats, restaurants and shops across four buildings in 2022.
However, this development never got spades in the ground.
In April, the joint venture company had contractors on site clearing overgrowth to allow more of the car park to be used.
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