DECATUR, Ga. -- The Georgia Bureau of Investigations believes it knows how a deadly drug spilled inside the back of a Duluth Police cruiser Wednesday, triggering a hazmat situation.

According to authorities, the drug fentanyl was being transported the 22 miles from the GBI's crime lab in DeKalb County to the Duluth Police Department, when the drug came out of its packaging.

"When they arrived at the police department to unload, they found out that some of that had spilled in the back," Duluth Police spokesperson Ted Sadowski said. "I’m not sure how long they were actually exposed to it....I’m not sure how it was packaged."

The drug fentanyl is so potent it can be dangerous if inhaled or absorbed through the skin. Two officers in the vehicle were exposed, but were disinfected at the scene.

PHOTOS | Fentanyl spilled at police department, Hazmat on scene

After an assessment, the GBI now believes that the fine-powdered drug leaked through untaped corners and seams of the cardboard box it was contained in.

The spill caused the GBI to temporarily halt the release of evidence and reexamine how evidence is packaged and transported. It released a statement following the incident saying:

The Georgia Bureau of Investigation’s Crime Lab is currently reviewing internal procedures for packaging drug evidence. This follows information received from the Duluth Police Department that evidence containing a fentanyl related drug spilled out of a package that was returned to the agency today. Additionally, the crime lab will be conducting a thorough review of this incident with the goal of establishing what caused the spill. A temporary hold has been placed on the release of all drug evidence during the review. An update will be provided following the full assessment.

The GBI said it now has now resumed the return of drug evidence. It has also modified lab procedures related to the packaging and return of drug evidence to make sure the situation is not repeated. Part of those new procedures include "enhanced sealing."

What is fentanyl?

Fentanyl has been in the news lately because of the fact that it's an ingredient in deadly street drugs that can be deadly on contact. The GBI has warned law enforcement agencies to take caution when responding to overdoses because the drug cocktail can be so potent.

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Fentanyl is a pain killer that’s about 100 times more potent than morphine. It’s often used as a pain reliever during surgery or for terminally ill patients.

In its powder form, one milligram - a grain about the size of a single piece of sea salt - is enough to cause an overdose.