The Federal Centers for Disease Control and Prevention reported that an illegal street version of the powerful painkiller fentanyl had claimed more than 1,000 lives in the last two years.

The fatal outbreak of overdoses occurred between 2005 and 2007 in several U.S. metropolitan areas, which was the first time illicitly produced fentanyl was linked to such a large increase in deaths in the U.S., as opposed to fatalities from heroin or other drugs commonly sold on the street.

Fentanyl is a potent prescription painkiller, prescribed to cancer patients or others suffering from severe, chronic pain and is often taken in the form of a patch or lollipop. Fentanyl can also be made by rogue chemists into a lethal narcotic powder, much more potent than heroin.

The illegal Fentanyl can be found mixed with cocaine or heroin or as a substitute for heroin on the street.

What first brought the matter to officials' attention was a cluster of deaths in Camden, N.J. but soon after health and law-enforcement officials identified similar waves in Chicago, Detroit, Philadelphia, St. Louis and other areas. The report tallied at least 1,013 deaths, although many more deaths likely went unreported.

The two-year outbreak significantly subsided after police shut down a fentanyl-producing operation in Mexico, which was suspected to be the main source of the illegal drug. However, the CDC say that painkillers continue to play a big role in fatal drug overdoses, and said deaths from unintentional drug poisonings doubled between 1999 and 2005.