CBS has concluded its reopened “Matlock” investigation into the sexual assault report that got David Del Rio canned from the series … and the actor is eager to know the outcome.

TMZ broke the news … Del Rio was booted from the hit show last October, after the star had been accused of sexually assaulting actress Leah Lewis on Paramount property days earlier. Del Rio vehemently denied the allegations, hiring high-powered attorney Shawn Holley… and CBS reopened its investigationin November and more parties were interviewed — including David himself alongside Holley.

Sources with direct knowledge tell TMZ … the investigation has concluded — again — but Del Rio feels the powers that be are dragging their feet after he claims to have submitted evidence that would clear his name. We hear he’s instructed his team to request that CBS give them their findings, which we’re told are expected by the end of this week.

Our sources say that Del Rio’s frustration stems from the fact his termination was basically instant … and the reopened investigation has taken 72 days. It’s worth noting, our Del Rio sources tell us both investigations were handled in-house by CBS Studios, not an independent third party.

In the fall, Del Rio was escorted off the Paramount lot and canned the same day the complaint was lodged … CBS Studios confirmed at the time his character — a lead in the series — would be written off. “Matlock” was recently renewed for a third season.