Police have said they were too busy to stop an illegal rave at an empty warehouse, which was attended by up to 1,000 people.
Officers were called to the unlicensed music event at Telford Way Industrial Estate, in Kettering, in the early hours of New Year's Day.
Northamptonshire Police said it was allowed to "run its course" because it was the force's busiest night of 2018.
The force added a "small number" of nearby residents complained.
Organisers promised it would finish by midday.
'So much bass'
An estimated 700 to 1,000 people had turned up to the event by the time police arrived, and officers monitored the site throughout the morning.
Supt Dennis Murray said: "I appreciate this has had an impact on people living near to the warehouse, and understand their frustration that we have not been able to close the event down.
"However, we have to consider other incidents taking place across the county and the resources available to us before taking action, and sadly New Year's Eve is by far the busiest night in policing.
"We will continue to monitor the situation and will investigate any criminal offences reported to us as a result of the event."
John Medley, who lives off Northfield Avenue, said: "It started about midnight. I noticed this background of drumming beats and it just kept going long after the sound of fireworks died away.
"I couldn't get to sleep because there was so much bass. You don't hear it, you feel it."