A federal judge on Wednesday stopped the scheduled execution of a serial killer in Texas, saying justice department officials must disclose information to the inmate's lawyers about the supplier of a new batch of drugs that would be used to kill him.

U.S. District Judge Vanessa Gilmore issued a temporary injunction stopping the lethal injection of Tommy Lynn Sells. He had been set to die Thursday.

State officials have insisted the identity of the supplier must be kept secret to protect the company from threats of violence.

Attorneys insist the name is needed to verify the quality of the drug and keep the inmate from unconstitutional pain.

Gilmore had ordered the Texas Department of Criminal Justice to provide to Sells's attorneys information about the drug procurement, supplier, testing, what kind and who conducted the testing.

Texas prison officials haven't provided them "with sufficient information," Gilmore said in her ruling Wednesday.

It was not immediately certain if lawyers for the state will appeal Gilmore's ruling.

Since obtaining a new supply of the drug pentobarbital two weeks ago, the Texas Department of Criminal Justice had cited unspecified security concerns in refusing to disclose the source and other details about the sedative it plans to use to put inmates to death.

But in a brief filed Tuesday with the state attorney general's office, Patricia Fleming, an assistant general counsel for the Texas prison system, argued that a supplier in another state received a specific threat of physical violence.

"An individual threatened to blow up a truck full of fertilizer outside a pharmacy supplying substances to be used in executions," Fleming wrote.

As such, she argued, an open-records request filed by an attorney for a condemned inmate seeking the drugmaker's identity should not be granted.

Questions about the source of drugs used by states to carry out lethal injections have arisen in several states in recent months as numerous drugmakers — particularly in Europe, where opposition is strongest to capital punishment — have refused to sell their products if they will be used to carry out executions.

That has led several U.S. prison systems to compounding pharmacies — pharmacies that make specific blends of drugs — which are not as heavily regulated by the U.S. Food and Drug Administration as more conventional pharmacies.

A batch of pentobarbital Texas purchased from such a compounding pharmacy in suburban Houston expired at the end of March. That pharmacy refused to sell the state any more drugs, citing threats it received after its name was made public. That led Texas to its new, undisclosed suppler.