The 27-year-old son of the owners of a Wesport trash-hauling business — missing since they were last seen in early August — has been indicted by a federal grand jury in Bridgeport.

Kyle Navin, son of Jeffrey and Jeanette Navin, the owners of Westport-based J&J Refuse, was indicted Thursday on a charge of possession of a firearm by an individual who is an unlawful user of and addicted to any controlled substance, according to an announcement from Deirdre Daly, the U.S. attorney for Connecticut.

The younger Navin, considered a “person of interest” in the investigation into his parents’ disappearance, was arrested Sept. 8 on a criminal complaint alleging violation of the federal gun law. He has been detained since his arrest.

The charge is based on two police searches of Kyle Navin’s Bridgeport home in August, as investigators looked for clues regarding the whereabouts of his parents, last seen Aug. 4.

According to Daly’s announcement, two firearms and numerous rounds of ammunition were seized in the first search. And during the second search, officials said they found “items indicative of substance abuse, including numerous heroin brand-stamped glassine bags with heroin residue, hypodermic needles, empty prescription bottles for oxycodone and prescription bottles containing other controlled substances.”

They also said they found a receipt from a firearms shooting range Aug. 5, the day after Navin’s parents were last seen.

Jeffrey and Jeanette Navin, who both attended Westport schools growing up in town, later lived in Weston and, most recently, were Easton residents.

The date for Kyle Navin’s arraignment on the firearm charge has not been set. If convicted, he faces a maximum term of imprisonment of 10 years.