A Ronkonkoma man was indicted on manslaughter and drug charges Tuesday for causing the overdose death of a customer to whom he sold drugs, Suffolk County prosecutors said.

The defendant, James Fava, 28, warned in text messages to the victim, Bryan Gallagher, also 28, that he was concerned about the potency of the opioid fentanyl he had sold to Gallagher, the district attorney’s office said in a statement.

Fava pleaded not guilty at his arraignment Tuesday before Judge William Condon in County Court in Riverhead. Condon set bail at $100,000 cash or $200,000 bond.

Fava is due back in court Jan. 17.

Prosecutors said later that Fava was arrested, “as a result of an investigation . . . developed regarding drug dealing occurring at 396 Wildwood Road.” Fava lived in the house with his parents.

Fava family members who attended the arraignment refused to comment as they left court. Defense attorney Noel Munier of Mineola also declined to comment.

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Gallagher’s family was also in the courtroom, as was District Attorney Thomas Spota. The family members did not comment as they left the courtroom.

Relatives of Gallagher found him dead in their home on July 18, a day after he bought drugs from Fava, prosecutors said.

A needle and a spoon were found next to this body, prosecutors said, and the cause of death was determined to be fentanyl intoxication.

If convicted, Fava faces a determinate sentence of between 1 and 9 years in prison on two drug charges, an indeterminate sentence of 5 to 15 years on the manslaughter charge and 1 1/3 to 4 years on a conspiracy charge, a spokesman said.

It was the second time Suffolk prosecutors have filed manslaughter charges in a case where the drug user died.

Roxy Headley, Jr., 29, of Mastic was indicted on a manslaughter charge in August for selling a lethal dose of heroin and fentanyl to an unidentified North Babylon man.

To convict on manslaughter charges prosecutors would have to prove that the defendant recklessly caused the victim’s death.