6:10 PM PT -- We're told one man was arrested inside the house for the crime of selling, possessing or transporting illegal assault weapons. We do not know if he was a squatter or had permission to live in the home. As we reported, the owner hasn't lived there in years and is now in Europe.

4:23 PM PT -- The ATF now says, "Pursuant to an anonymous tip ATF and LAPD became aware of an individual conducting illegal firearms transactions outside the scope of the federal firearm license that the individual possesses." The ATF says they have seized more than 1,000 firearms, adding the public is in no danger.

A massive stockpile of firearms has just been confiscated in a super rich area of Los Angeles ... and the sheer number of guns is jaw-dropping.

The weapons were recovered after a search warrant was served at a home in Bel-Air ... and the huge pile of guns are currently being laid out on the street.

It's all going down right now, near the Playboy Mansion and close to the estate where Michael Jackson died.

Cops got a tip that someone was in the house selling and manufacturing weapons. They are on scene right now.

There are 3 SUV's in the driveway and we know at least 2 are registered to a Cynthia Beck, who also owned the home and may still own it. We do not know if there is any connection between her and the weapons or the search warrant.

A person familiar with the neighborhood tells TMZ, Cynthia hasn't been seen at the house in years, and may be in Europe. The person adds there have been "caretakers" coming and going at the estate. It well could be ... someone knew Cynthia wasn't in the country and squatted in the house.

The Federal Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) is the lead agency. We're told they were doing surveillance Wednesday morning before making their move and they are still on the scene.

Our LAPD sources tell us as far as they can see they have not had any problems associated with the residence in question.