ATLANTA - All Georgia executions are off after federal drug agents seized the state's supply of a sedative used in lethal injections that has been challenged by capital punishment critics and death-row inmates, including a man recently executed who called the British exporter of the drug a "fly-by-night supplier."

Drug Enforcement Administration spokesman Chuvalo Truesdell wouldn't say exactly why Georgia's supply of sodium thiopental was taken Tuesday, just that "we had questions about how the drug was imported to the U.S." The sedative is part of a three-drug cocktail used in executions that has been in short supply since the sole U.S. manufacturer stopped making it.

No more execution dates in Georgia have been scheduled and it's unlikely any will be set before the issue is resolved. Georgia Attorney General's Office spokeswoman Lauren Kane said prosecutors couldn't ask a judge to set executions if corrections officials didn't have the necessary supplies to carry one out.

Georgia's stockpile of the drug has been a target of death row inmates and capital punishment critics since corrections officials released documents this year showing the state obtained the drug from Link Pharmaceuticals, a firm purchased five years ago by Archimedes Pharma Limited. Both are British firms.

The drug was used in January to execute Emmanuel Hammond, a 45-year-old man convicted for the 1988 shotgun slaying of an Atlanta preschool teacher. His attorneys sought a delay to gather more information on how the state obtained the drug, claiming in court documents it came from a "fly-by-night supplier operating from the back of a driving school in England." They said the drug could have been counterfeit.

The U.S. Supreme Court, as well as lower courts, rejected Hammond's argument.

The state's stockpile came under more scrutiny in February when John Bentivoglio, a former deputy attorney general, asked the Justice Department to launch an investigation into whether state corrections officials violated federal law by not registering with the DEA when it imported its supply of sodium thiopental.

"The United States has strict drug import rules for a reason: To ensure drugs used for legitimate purposes are not adulterated, counterfeit, or diverted into the illicit market," said Bentivoglio, who is representing death row inmate Andrew Grant DeYoung.

Joan Heath, a spokeswoman for the Georgia Department of Corrections, said state officials were not concerned with the quality of the drug and just wanted to make sure they were complying with the law.

"We contacted the DEA and asked them for a regulatory review, and that's what we're doing," she said. "We're going to make sure we're in regulatory compliance with the DEA over how we handle controlled substances."

Hammond's attorney, Brian Mendelsohn, declined to comment.

A third death row inmate has also targeted Georgia's supply. Roy Willard Blankenship's attorneys asked a judge in February to call off his execution until the state released more details of its 20-gram supply of sodium thiopental. The complaint contended that an expired drug may not fully put Blankenship to sleep - which could make his death extremely painful.

Blankenship's execution was delayed in February after the Georgia pardons board granted his lawyers more time to conduct additional DNA testing.

Link Pharmaceuticals didn't exist in 2010, and its name hasn't been on labels since May 2007, the lawsuit said. Sodium thiopental typically has a shelf life of four years, meaning even the state's newest supply would expire in May of this year, the lawsuit claims.

A federal judge rejected Blankenship's arguments as "nothing more than unreasonable speculation." He added that even if Blankenship could prove the supply expired, he failed to show it "creates a risk that is sure or very likely to cause serious illness or needless suffering."

The shortage has delayed executions in several states and an Associated Press review found that at least five states - Arizona, Arkansas, California, Georgia and Tennessee - had to turn to England for their supply of the drug. Nebraska, meanwhile, secured a stockpile from an Indian firm.

Truesdell, the DEA spokesman, said he was not certain if other states' supplies of sodium thiopental were also being collected by the agency. Officials in Arkansas and California said authorities have not seized their supplies.

Defense attorneys were elated by the news.

"We commend the DEA for forcing the Department of Corrections to immediately cease using black market execution drugs," said William Montross, an attorney with the Southern Center for Human Rights, which had sought to delay Blankenship's execution.

"It is an incredible relief that this federal agency has stepped up and intervened where the state and federal courts have turned a blind eye to the obvious problems with the procurement and use of these drugs."