Abandoned tents and litter were found at a Lake District beauty spot ahead of lockdown travel rules being eased.
Volunteers cleared the site at Thirlmere, Allerdale, on Sunday amid fears people are travelling to the National Park for overnight stays, which are banned until 12 April.
Those responsible have been identified and their details passed on to police.
An influx in tourists after the first lockdown last year saw roads blocked and litter dumped in some areas.
In England self-catering accommodation and some campsites are able to reopen from 12 April but hotels and B&Bs cannot resume trading until 17 May at the earliest.
“What we are really concerned about at the moment is people coming for overnight stays as there is no accommodation open,” said Assistant Chief Constable of Cumbria Police Andy Slattery.
“There were only a small number of incidents at the weekend but if you multiply that as we had last spring and summer then the impact on the area is quite significant.
“That sort of behaviour has started and we really want to nip that in the bud so people don’t indulge in that.”
Volunteers cleaned up the makeshift site, collecting 13 bags of rubbish.
Details of those who left it were found and have been passed on to police in Cumbria and Merseyside.
Nicola Bolton, who runs The Lakes Plastic Collective Facebook page, said the mess was “very disappointing” and it showed a “sheer disrespect” for the area and those who live there.
“Not all visitors behave this way thankfully but I don’t think this will be the last of scenes like the one at Thirlmere over the weekend,” she said.
“People should follow the countryside code and always leave no trace.”
The Lake District National Park Authority said talks had been held with the government to avoid a repeat of 2020, when it had to “scramble” teams to reopen basic facilities such as car parks and toilets due to short notice.
Richard Leafe, chief executive, added that it would be “inevitable” there would be some repeat of scenes from a year ago.
“We only ask people to come if they can safely return home at night,” he said.
“I appreciate it didn’t necessarily get off to a good start at the weekend and I think inevitably, with the sheer volume of people we are going to have, there will be some repeat of what we saw.”