IOWA CITY, Iowa -- Former NFL and Iowa safety Tyler Sash died from an accidental overdose after mixing two powerful pain medications, and a history of painful injuries was a contributing factor, a medical examiner said Tuesday.

Additional studies will look at whether Sash, 27, suffered from chronic traumatic encephalopathy, a brain disease caused by repetitive trauma that has been found in several former NFL players. The results will be available in eight to 12 months, according to a statement from the Iowa State medical examiner's office.

Sash, a standout safety at Iowa who won a Super Bowl during his rookie season with the New York Giants in 2012, was found dead at his home in Oskaloosa, Iowa, on Sept. 8. An autopsy was conducted the next day, but the results weren't clear until laboratory results were completed.

The autopsy determined the cause and manner of death was an "accidental mixed drug toxicity involving methadone and hydrocodone," the office said Tuesday. Both are legal narcotics used to relieve severe pain, but are also highly addictive.

The medical examiner said that a recent shoulder dislocation and a history of chronic shoulder pain suffered by Sash were also "significant conditions" in the death.

Oskaloosa Police Chief Jake McGee said investigators learned that Sash had a doctor's prescription for hydrocodone but are not sure about how he obtained methadone.

Polly Carver-Kimm, a spokeswoman for the medical examiner's office, said she couldn't release any additional information about the pending CTE testing, including where it would be conducted.

Sash played two seasons with the New York Giants. Months after the Super Bowl victory, he was suspended for four games in 2012 for violating the NFL's performance-enhancing substances policy by testing positive for Adderall, a stimulant used primarily to treat attention deficit hyperactivity disorder and the sleep disorder narcolepsy. The Giants cut ties with Sash before the 2013 opener, reaching an injury settlement after he sustained a concussion in the preseason finale against New England.

At Iowa, Sash started 37 games for the Hawkeyes from 2007-10, earning first-team All-Big Ten honors in his final season. He bypassed his fourth year of eligibility to enter the NFL draft.

Iowa coach Kirk Ferentz told reporters Tuesday that he was "very sorry to learn about" Sash's cause of death.

"His passing has been a very, very sad thing," Ferentz said.