The bust happened inside a warehouse behind a home near Grantland and Ashlan avenues, which is just down the street from Justin Garza High School.
On Thursday, detectives with the Fresno County Sheriff's Office learned of possible illegal drug sales thanks to a recent tip from Valley Crime Stoppers.
Distributors connected to operation called the event Sunday Funday.
Detectives say they have learned the events date back as early as the beginning of the year.
"What we found inside was a full on set-up. Basically, think of like a baseball card show or a record show and you go in and its different types of drugs," said Tony Botti with the Fresno County Sheriff's Office.
The discovery led to a treasure-trove of drugs, including the seizure of 400 pounds of marijuana, 120 pounds of THC edibles, and small amounts of cocaine, ketamine, and Xanax.
The seizure also included the recovery of four handguns.
In total, Fresno County Sheriff's Office arrested four men and questioned as many as 30 people.
None of those arrested are minors.
Jason Oxford, who lives just down the street, says that every Tuesday and Thursday night, a dirt lot outside the building would be covered with parked cars and hundreds of people.
Oxford said he isn't surprised by the discovery.
"Every Tuesday night I could say for sure, there's a gentleman out here usually stands when they're going in and out with a vest on," explained Oxford.
"He says he's security, but when you ask him what's going on, they just say it's a private event."
"This is your home and you want it to be a nice, clean, safe environment, step up. If you know something, let us know about it because we're going to look into it," Botti added.
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