India, Jan. 23 -- The Federal Bureau of Investigation (FBI) are focusing its investigation into the death of former Indianapolis Colts owner Jim Irsay by looking into his substance use and medical treatment.

Irsay's recovery specialist, Harry Haroutunian, who treated him in his final days, is suspected of having given him high doses of opioids and ketamine, according to a Washington Post report.

According to reports, the FBI issued grand jury subpoenas seeking medical records, correspondence and information about Irsay's substance use and his relationship with his doctor, Haroutunian.

Federal agents reportedly visited Indianapolis earlier this month to interview people close to Irsay and gather evidence.

Despite his public declaration...