The U.S. Supreme Court won't stop the execution of a Texas serial killer whose attorneys want the state to release information about where it gets its lethal injection drug.

Tommy Lynn Sells' lawyers' plea to the high court was rejected about an hour before his scheduled execution Thursday.

A lower court had stopped the execution earlier this week and ordered Texas to reveal more information about its drug supplier. But that ruling was tossed on appeal.

Sells' attorneys say they need to know the name of the pharmacy providing Texas' pentobarbital, the drug used during executions, in order to verify its quality and protect Sells from unconstitutional pain and suffering.

Texas prison officials say drug supplier information must be kept secret to protect the provider from threats of violence.