An illegal New Year rave at the former Focus DIY store in Sopwith Way, Daventry, was attended by around 1,200 people.
The event, which is thought to have begun on the industrial estate around 2am on January 1, was closed down by police at noon later that day.
Jared Thompson, who lives on the Timken estate, was walking his dog along Sopwith Way at 6am on January 1.
He said he saw at least 50 cars on the road leading to the Focus store: “Both sides of the road around the unit were chock a block with cars and vans. I saw alot of people asleep in their cars and some kids were throwing up outside. By the time I got there my dog was getting really wound up.”
“I saw the concrete blocks blocking the gates of the Focus site had been moved out of the way.
“It wasn’t a good atmosphere; I wasn’t going to stick around.”
Mr Thompson, who works as a transport clerk at the DHL Wetherspoons warehouse on Nasmyth Road, said when he walked past the site again at 10.30am the area had been blocked off by police.
“There was still a mess there when I walked past. There were puddles of sick, bottles and empty boxes of Stella. It was a bit of a pigsty really.
“I think it is disgraceful, maybe I’m a bit old fashioned but I never did something like this when was young.”
The concrete blocks securing the site have now been replaced and contractors are working to clear the rubbish.
Inspector Michael Smith of Northamptonshire Police said: “To date, no arrests have been made, however details of the organisers have been taken and further enquiries are taking place at this time.”