Liam Payne Death Investigation, Focus on Drugs and Soap Box Found in Room

One small item found in Liam Payne‘s hotel room is getting a lot of attention from cops investigating his death, because it might unlock the mystery of who helped him score drugs … TMZ has learned.

Law enforcement sources in Buenos Aires tell us … authorities are now investigating the possibility a hotel employee delivered drugs to Liam, which has them focusing on a Dove soap box found in the room, and seen very clearly in a photograph taken after Liam’s deadly fall.

The box was on the same table where cops also found drugs and paraphernalia — tinfoil used to ingest drugs, as well as white powder.

We broke the story … cops have been looking into hotel employees for several days now — with sources saying they’ve got one particular worker in their crosshairs for allegedly giving Liam the anti-anxiety medication they found.

Cops were also investigating whether that employee gave LP the cocaine, crack, ketamine, ecstasy and a form of crystal meth called “cristal” the initial autopsy found in his system.

Late last night, cops raided the Buenos Aires hotel where Liam died … reviewing electronic and paper records — all to figure out who sold the former One Direction star the drugs.