More than twice as many people in the Tucson region died of methamphetamine overdoses last year than in 2011 and 2012 combined, according to an annual report from the Pima County Office of the Medical Examiner.

Deaths due to heroin overdoses likely are following the same trend, but those deaths can be harder to track, said Dr. Gregory Hess, chief medical examiner for Pima County.

His office investigates any death that is sudden, violent, unexpected or where the cause of death is unknown. Last year, the office conducted nearly 1,500 autopsies, the report states.

Almost three-quarters of the 2,333 death cases reviewed by the local medical examiner in 2013 were from Pima County. The office also handles all cases for Cochise and Santa Cruz counties. Eight other counties use the office’s services on a case-by-case basis, Hess said.

In cases handled by his office last year, 327 deaths — a slight year-over-year increase — were determined to be overdoses of drugs or alcohol. In about half of those deaths, the overdose was caused by a single drug. The majority of the deaths — 87 percent — were classified as accidents.

In 2012, the medical examiner reviewed the cases of 314 overdose victims. In 2011 and 2010, the number of overdose deaths was 277 and 273, respectively.

The most significant difference over the last couple of years was in the types of drugs contributing to overdoses.

For several years previous, oxycodone, a painkiller that can be highly addictive, was identified as causing the most overdose deaths in the Tucson area.

However, last year, meth “was the most commonly abused illicit drug contributing to death … followed by heroin; both significantly increased in comparison to 2012,” the medical examiner’s report stated.

Meth contributed to 78 deaths in 2013.

Morphine was listed as the second-highest killer, playing a part in 64 deaths, followed by oxycodone found in 55 victims, but it is likely that heroin actually caused more than the 53 deaths ascribed to it.

“Heroin is probably on par with meth, but we can’t prove that,” Hess said. “The number of heroin deaths is likely underreported.”

That’s because heroin is rapidly metabolized to morphine by the body, so some of these “deaths may be classified as either morphine intoxication or opiate intoxication,” he said in the report.

Demographically, 58 percent of those who died of a fatal overdose were men, and about half the people who died of an overdose were between the ages of 40 and 59. Fifty-six of the 327 reported overdose deaths were people 20-29 years of age; seven were teenagers.

Nearly 1,700 deaths reviewed by the Medical Examiner’s Office occurred in Pima County last year, according to the annual report.

The highest number of deaths — 657 — were attributed to natural causes. The leading cause of natural death was cardiovascular disease.

Of the 123 homicide victims examined, 88 of them were killed in Pima County. That was down from 136 cases in 2012 — 79 in Pima County.

The largest number of victims, 34, were between the ages of 20 and 29, and the majority of the victims — 80 percent — were men. Of the homicide cases, 62 percent were from firearms, with stabbings and blunt-force trauma tied for second most.

From all counties, the medical examiner reviewed 843 cases of accidental death. Overdoses, blunt-force trauma and motor-vehicle accidents were the top three causes of accidental deaths last year.

Of the 199 deaths ascribed to vehicular accidents, 120 were in cars or trucks, 35 were on motorcycles and 44 were pedestrians or bicyclists.

Of the 270 suicides reported by counties that asked the Pima County medical examiner for assistance, 213 of the victims were male. Almost 200 of the people who killed themselves ranged in age from 20 to 59.

The skeletal remains of undocumented border crossers made up a majority of “undetermined” deaths in the medical examiner’s report. Of the 168 sets of remains recovered in 2013, forensic anthropologists determined most were men from Mexico. The number of recoveries was down from a high of 223 in 2010, according to the report.