Partygoers breaking lockdown rules said they "never watch the news" so were unaware of the global coronavirus pandemic, police said.
Officers were called to an illegal party in Guernsey Close, Basingstoke, at 20:30 GMT on Saturday.
In a tweet, Hampshire Constabulary said those present were spoken to, adding the hashtag "#ThereAreNoWords".
Under coronavirus laws, police in England have the power to issue fines of £200 to first-time offenders.
This can go up to £10,000 for holding, or being involved in holding, an unlawful gathering of more than 30 people.
Hampshire police said an investigation was under way "with a view to reporting the individuals involved for summons following a Covid breach".
'Take this seriously'
The force has called on everyone in the county to observe the rules, adding that people were found to have travelled from Dorset and Surrey to the New Forest.
In a Facebook post, it said officers on Covid patrols over the weekend reported "every single" car park in the New Forest was "ram packed with vehicles".
It added: "When members of the public were asked where they have travelled from, some said that their home addresses are in places such as Guildford and Dorset."
The post warned: "We are in a lockdown, you should only be travelling locally. Guildford is over 55 miles from the New Forest. This is not local."
It urged people to "please take this seriously", use common sense to decide what "local" means and "stick to your town/city".