The Texas attorney general ruled on Thursday that the state's prison system does not have to disclose which pharmacies supply lethal injection drugs used for executions, showing a change of opinion by the state's premier prosecutor.

The decision goes against the tide of the recent challenges in death penalty states to reveal where the execution drugs come from, The Associated Press reported.

Attorney General Greg Abbott had previously rejected three similar attempts by the Texas Department of Criminal Justice to keep the source of the drugs used in executions a secret.

On Thursday, Abbott showed a reversal of opinion by siding with prison officials who said that revealing the supplier of the drugs could be dangerous if disclosed. Their claim was corroborated by a "threat assessment" that was signed by Steven McGraw, the Texas Department of Public Safety director.

The one-page assessment said pharmacies "by design are easily accessible to the public and present a soft target to violent attacks." He said that naming the pharmacies that supply execution drugs "presents a substantial threat of physical harm ... and should be avoided to the greatest extent possible."

The decision made in Texas, the state with the most executions, came on the same day that Missouri Attorney General Chris Koster said his state should create its own laboratory to make execution drugs instead of relying on outside suppliers.

Both Missouri and Texas claim that disclosing the places that supply their execution drugs must be kept secret so suppliers are not threatened with violence. Conversely, attorneys representing death row inmates say the need the information to verify the drugs' efficacy and protect their clients from cruel punishment.

Neither the U.S. Supreme Court nor state courts have stopped an execution because of states' refusal to disclose where they get drugs for lethal injections. The secrecy defense was used in Oklahoma before a botched execution, although the inmate's veins, not the drug, was blamed as the reason for the mishandled execution.

Texas, unlike other states, does not say whether or not prison officials must disclose where they buy drugs for execution.

According to a Department of Public Safety assessment, the owner of the pharmacy that supplies Texas' execution drugs complained of "constant inquiries from the press, the hate mail and messages." While the agency said that the threats should be taken seriously, they did not say that those threats are under investigation.

Earlier in the month, the AP and four other news agencies filed a lawsuit against the Missouri Department of Corrections, saying the state's refusal to disclose where they get their execution drugs violates the public's right of access to information.

Many states have been turning to compounding pharmacies for lethal injection drugs after many drug makers, many of whom are based in Europe, refused to sell the drugs. The compounding pharmacies are not as regulated by the Food and Drug Administration as are regular pharmacies.

Abbott's decision is expected to be appealed and could go to the Texas Supreme Court.