Katt Williams Arrest -- Cops Say Gun Found Was STOLEN

Katt Williams has some explaining to do ... because cops now say one of the guns seized from the comedian's house during his most recent arrest was recently reported stolen.

TMZ broke the story ... Katt was arrested Friday on charges of child endangerment after an investigation from the L.A. County Dept. of Children and Family Services concluded there was a slew of guns and illegal drugs stashed in his house.

Now the LAPD is telling the LA Times​ that one of the firearms taken from Katt's crib was reported stolen.

Immediately following Katt's arrest, he told TMZ he kept his guns in a locked box and it was his right as an American to possess firearms to keep his kids safe.