Officials in Detroit and Ann Arbor are on high alert after a sharp increase in drug overdoses involving the prescription painkiller fentanyl.

So far this year, about a third of all drug-related deaths in Washtenaw and Wayne counties have been fentanyl-related, according to a release from the University of Michigan Health System.

"We are increasingly seeing signs of what appears to be a return to the epidemic levels of 10 years ago, when fentanyl-related drug overdoses were blamed for 236 excess drug deaths," Washtenaw County Medical Examiner Dr. Jeffrey Jentzen said in a statement

It's a trend that's been seen across the country at toxicology laboratories, Jentzen said.

The University of Michigan Health System Department of Pathology runs the medical examiner offices in both counties.

Overdoses involving the drug have killed 58 people in both counties since January, according to the release.

For comparison, a total of 68 deaths from fentanyl combined with heroin, other prescription painkillers, alcohol or cocaine, or several, were recorded for the entire year of 2014 in Wayne County, the Health System reported.

Now in 2015, the county has already seen 53 similar deaths.

Combinations with opiates, such as hydromorphone or oxymorphone, have been most common in the deaths, but more than 20 have been heroin-fentanyl combinations.

Heroin combinations have been of higher concern in Washtenaw County.

Of the 23 heroin-related deaths in the county since October, seven involved combinations with fentanyl, according to the release.

Just this year, two people died in the county after injecting pure fentanyl, believing it was heroin, according to the system.

Jentzen said doctors use fentanyl as an anesthetic or to treat severe cancer pain, but it can be dangerous alone or combined with other drugs.

"This combination kills even experienced drug users, who likely do not know that they're consuming a drug that's 15 to 20 times more potent than heroin, and 80 to 100 times more potent than morphine," Jentzen said.

He said the painkiller is used to cut heroin to reduce costs.

"Fentanyl decreases breathing to the point that you can 'die before you get high,' and yet does not produce the high that users seek," Jentzen said.

He said even when heroin or opiate painkiller overdoses are treated, people using combinations with fentanyl can still die because it has a longer half-life in the body.

A nurse at the health system died last year from an overdose involving combined with another drug.

Because of the increased fentanyl overdose deaths, Jentzen and Wayne County Medical Examiner Dr. Carl Schmidt, a University of Michigan associate professor, are asking medical personnel to check for longer-term effects and calling for awareness in the community, according to the release.