SHIRLEY, MASS. (WHDH) - The Shirley prison where Aaron Hernandez was found dead last week remains on lockdown as investigators search for evidence related to the ex-New England Patriots tight end’s death.

Officials at the Souza-Baranowski Correctional Center in Shirley, where authorities said Hernandez hanged himself with a bed sheet, said the prison has been locked down to accommodate a “special operations search.” The Massachusetts State Police are leading the effort.

RELATED: Lawyers want Aaron Hernandez’s murder conviction dismissed

Sources told 7News that officers were searching cells for contraband in connection with Hernandez’s death, including synthetic marijuana, which can be smuggled by dipping paper into the liquid drug and mailing it in an envelope.

Attorneys representing Hernandez also filed a motion Tuesday, formally asked that his first-degree murder conviction be dismissed in Massachusetts now that he has died. Hernandez was found guilty in 2015 of murdering Odin Lloyd and was serving a life sentence for it at the time of his death. Courts in Massachusetts have held that when a defendant dies before having an appeal heard, the conviction is vacated.

In a rare movie, New Bedford District Court judge Thomas McGuire released audio transcripts from a sidebar discussion between Hernandez’s lawyers and Secretary of Public Safety Daniel Bennett.

“It’s going to be in lockdown. I actually don’t want to say how long it going to be in lockdown. But it’s in lockdown and one of the reasons is because of the issues with Mr. Hernandez and things that have happened with Mr. Hernandez,” Bennett was heard saying.

Those issues reportedly centered around Bennett’s concern about the release of the suicide notes that were found in Hernandez’s cell.

“I don’t even know, I have never seen those letters. I have a police report with references to the three letters and a reference to how he’s going to be. Essentially don’t cry for him. He’s going to be happy in the afterlife,” said Bennett.

RELATED: Aaron Hernandez’s suicide notes released to family on judge’s order

Correctional officials are not allowing guests inside the prison walls as the search continues. It is not clear what investigators found or when the lockdown will be lifted.

On Monday, three suicide notes that were found in Hernandez’s cell near a Bible were released to his family, per order of a New Bedford District Court judge.

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