Jefferson Parish Sheriff Newell Normand called a news conference Thursday to publicize the results of a six-month undercover operation launched after the department received a tip that firefighters were using and selling drugs in sparsely populated Grand Isle.

In all, 20 people were arrested, most on misdemeanor charges of possessing marijuana or drug paraphernalia. Only two were firefighters.

One of the targets apparently was the chief of the volunteer Grand Isle Fire Department, 40-year-old Aubrey “T-Black” Chaisson. Deputies arrested him after seizing a “very small amount of marijuana” during a search of Chaisson’s home, Normand said. He was booked with marijuana possession and an outstanding warrant for contempt of court.

Another firefighter, Patrick Santiny, 50, was booked with possessing a controlled dangerous substance, marijuana and drug paraphernalia.

During the probe, investigators camped out in a hotel in Golden Meadow in nearby Lafourche Parish and traveled into Grand Isle to make undercover buys.

Normand said the small, insular nature of the island made the undercover work tough.

“Every time a new face is seen down there, everybody’s antenna goes up and their radar is on and it makes it very, very difficult,” he said.

He said it was not yet clear if the two firefighters were using drugs on the job.

According to Normand, the Sheriff’s Office also had received information about financial mismanagement in the fire department, which it was reviewing. The department draws funding from its own dedicated property tax and works on a contract with Jefferson Parish.

Normand said Lafourche sheriff’s deputies, who along with State Police assisted in the investigation, seized 15 guns during the investigation from a man who was a felon. Deputies also booked two people on possessing methamphetamine and arrested one man on distribution of prescription pills.

The owner of Artie’s Sports Bar, a hub for drug transactions, according to Normand, also was cited after underage undercover officers purchased alcohol at the bar.

Deputies were still looking for two suspects, Cougar Walker and Michael Foxworth.

The sheriff said the investigation revealed a culture of casual, open drug use on the tiny island with a full-time population of about 1,000.

“Conversations about marijuana use and some other drugs are fairly wide open down there,” Normand said.