A 36-year-old inmate was found unresponsive in his Lake County jail medical unit cell Friday and was later pronounced dead at a local hospital, the Lake County Sheriff’s Office announced.

Lake County Sheriff Mark Curran and Undersheriff Ray Rose said a recently instituted new protocol regarding any jail deaths requires the Lake County Major Crime Task Force to conduct an independent investigation. The county has had four inmate deaths over the past five years, including one where a woman jailed for missing jury duty went on a hunger strike and died. The latest death brings the number to five.

An autopsy Friday afternoon by the Lake County Coroner’s Office revealed the preliminary cause of death appears to be natural causes, pending final toxicology results, according to a statement. There were no signs of internal or external trauma to the inmate’s body, the release said. The inmate’s name was not released.

The man was brought into custody on Feb. 29 after being arrested on an arrest warrant for failing to appear in court on charges of possession of a controlled substance. While in custody he told jail officials he was feeling ill from drug withdrawal. He was placed under the care of the jail medical unit, the statement said.

On Friday morning he was found unresponsive in his cell inside the medical unit. Staff began administering aid and an ambulance was summoned. He was transported to Vista Medical Center East, Waukegan, where he was pronounced dead.

The protocol of calling in the Major Crime Task Force was designed to initiate an immediate thorough independent investigation of the facts surrounding the death and produce increased transparency, the statement said.

The Lake County jail has been rocked by inmates deaths over the years that also prompted lawsuits.

In 2014 inmate Igor Karlukov, 36, of Palatine and a Ukraine national, was found hanging inside his jail cell after he used shredded pieces of a mesh laundry bag and a piece of copper wire from a set of ear buds to hang himself from a vent, despite the fact he was on special watch.

He had been told by a judge that he could face life in jail for charges related to a home invasion and domestic battery against his girlfriend.

Two of the jail’s inmates died in 2012.

Lyvita Gomes, 52, a native of Mumbai, India, who was living in Vernon Hills, launched a 15-day hunger strike to protest her incarceration for failing to appear for jury duty, then died of malnutrition and dehydration less than a week later.

Eugene Gruber, 51, of Grayslake, suffered paralyzing neck injuries while struggling with officers in the jail, then died months later after being transferred to a Chicago rehabilitation center.

The county agreed to settle a nearly $2 million federal lawsuit filed by Gruber’s family. The Cook County Medical Examiners Office in Chicago ruled Gruber’s death a “homicide,” but an investigation by the Lake County State’s Attorney’s Office found no wrong doing on the guards’ part.

The Gomes family also filed suit.

In 2011, there was a jail death when Thomas Arvie, 50, of Waukegan, apparently suffered a stroke in his cell. He died Sept. 22, 2011.

In 2008, Curran spent a week as an inmate that garnered national attention.