Police Searched Nick Reiner's Hotel Room for Murder Weapon in Reiner Murders

An LAPD Robbery-Homicide detective showed up at the hotel where Nick Reiner was staying … looking for a weapon, blood, and other evidence connected to the murders of Rob and Michele Reiner … TMZ has learned.

A law enforcement source, along with two other people with direct knowledge, tell TMZ ... a Robbery-Homicide detective showed up at The Pierside Santa Monica hotel Monday around 1 AM, telling the front desk clerk he was there to investigate Nick Reiner's room.

We’re told the detective said he was concerned Nick may have disposed of a weapon connected to a violent crime. The detective also said he believed Nick may have "cleaned up" and "disposed of evidence." We’re told hotel staff took the detective up to room 207, where he searched the room.

TMZ broke the story … a housekeeper cleaned up Nick's room late Sunday morning, where she discovered blood in the shower as well as blood on the bedsheets.

We also have more details about Nick’s check-in ... as we reported, when he checked in at 4:15 AM Sunday, a hotel staffer believed he was "tweaked out." We're now told that staffer believed Nick was high on some sort of stimulant.

Our sources say at the time Nick checked in, he bought 4 Heineken beers and a bottle of water that were inside the hotel lobby shop. We’re told the beers were nonalcoholic, but it’s unclear if Nick knew that.

Our sources tell us room 207 was immediately sealed off by LAPD, and now we’re told the entire second floor has been sealed as the investigation continues.