Police issued £94,000 in fines for illegal gatherings in South Yorkshire over Halloween weekend.
Any large gatherings are banned under lockdown rules.
Nine fines of £10,000 were handed out at parties in Sheffield on Saturday, and a rave in a disused warehouse was broken up on Sunday morning.
South Yorkshire Police said the gatherings were “extremely irresponsible”.
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The three Halloween parties in Sheffield, at Endcliffe Crescent, Club Garden Road and Stalker Lees Road, were issued with maximum fixed penalties, police said.
One party had more than 70 people and a woman in fancy dress was captured on body camera saying she should be at home self-isolating.
“We fully appreciate how difficult the last few months have been and this current situation is incredibly frustrating for everyone,” said Supt Paul McCurry.
“However organising house parties at a time when the infection rate is rising so rapidly is extremely irresponsible.”
In Barnsley, police handed out 20 fines of £200 at a gathering in Ingbirchworth in the early hours of Saturday.
At the rave with 300 people in Kelham Island in Sheffield a 17-year-old boy was arrested on suspicion of obstructing police.
Officers are searching for the organiser.
“We must reduce the spread of the virus between different households… we all need to do our bit to slow the spread of this virus, and protect our health service,” Mr McCurry said.
“I hope this serves as a warning that where necessary, we will take action against those who show a clear disregard for the measures which are in place to protect others.”
Greg Fell, Sheffield’s director of public health, said it was “impossible to say how much damage had been done”.
“The more humans mix, the more opportunities there are for the virus to spread, it’s as simple as that.”
He said people could have the virus but not yet have symptoms and said gatherings must not happen “under any circumstances”.