Police have made one arrest and seized equipment following an unlicensed music event in Theydon Bois.
Officers were called to the scene shortly before 11pm on Saturday after reports of an event in a field off Forest Drive which had attracted up to 200 people.
They were met with some hostility and had objects thrown at them.
Shortly after 1am the music was turned off and larger crowds began to leave.
Among the items seized by officers were a set of decks, speakers and a generator.
One man has been arrested on suspicion of a breach of coronavirus legislation.
Chief Superintendent Tom Simons said: “Essex Police does not tolerate attacks, no matter how minor, upon officers who are just doing their job by responding to incidents reported to them by the public.
“In this instance, thankfully no officers were injured and the attendees did eventually disperse when they were asked to do so and that is a credit to the officers who attended the scene and worked under very difficult circumstances.
“As a result of our initial investigations, we have seized a number of items of musical equipment and one man has been arrested.
“The investigation is in its early stages and where action is required, we will take it.”