THOMASTON – A Maine State Prison inmate who was found dead in his cell May 23 died of acute methadone toxicity, according to the State Medical Examiner’s Office.

Warden Jeffrey Merrill said Thursday that he had just received the medical examiner’s report on Thomas Thurston’s cause of death. He said methadone is not a drug prescribed to inmates at the Thomaston prison. “We do not use it at our faciity,” Merrill said.

Thurston, 35, was serving a total of 21 years for numerous convictions, which included armed robbery, he said. Thurston’s convictions were from Springfield, Mass., where he was sentenced to 16 years for armed robbery, Merrill said, noting that he also got a consecutive five-year sentence for other crimes. His offenses included armed robbery, robbery, multiple assault and battery and multiple larceny, he said.

Before being transferred to Maine State Prison in 1996, Thurston had been incarcerated at Walpole State Prison in Walpole, Mass., for three years, according to Merrill. Thurston had a projected release date of August 2008. Merrill didn’t say why Thurston was transferred to the state, but the inmate did have family in Maine. The family was notified of the cause of death by the medical examiner’s office, the warden said Thursday.

Because the Thomaston prison does not dispense methadone, Merrill said the drugs would have had to have been smuggled into the facility.

“Obviously, there’s opportunity for smuggling,” he said, despite efforts by guards to shake down prisoners in search of contraband.

“We’re always watching,” Merrill said, adding that when inmates are given medications, guards check to make sure the drugs are ingested. However, sometimes prisoners manage to “cheek” the medications, he said, which is holding them in their mouths without swallowing them.

In that way, an inmate could potentially horde drugs, which could result in them taking too many at one time, he said. However, in Thurston’s case, he said, methadone had not been provided by the prison.

Methadone is used to treat heroin addiction, a local pharmacist said, but it is also prescribed for pain relief. Cancer specialists use methadone for pain relief, he said, noting that it does not provide much of a “high.”

The warden did not expect to conduct an investigation into Thurston’s case, adding that his death occurred more than six months ago. Prison staff discovered that Thurston was dead while doing routine cell checks.