Six Americans who were imprisoned in Kuwait have been released in an agreement with the United States, a representative for their families confirmed to ABC News.

The Americans, many of whom are veterans and former military contractors, were convicted on drug charges, Jonathan Franks, a crisis management consultant, said.

For years, however, the prisoners have "vigorously" maintained their innocence, Franks said.

Several more prisoners are expected to be freed in the coming weeks as part of the agreement, Franks added.

"This morning, the Kuwaiti government released six of my clients as part of an agreement that will ultimately free fifteen of my clients in short order. Each was convicted on drug charges, and each vigorously maintains their innocence," Franks said.

Convictions for possession of drugs in Kuwait may include long jail sentences or the death penalty, according to an advisory by the U.S. State Department.

ABC News has reached out to the State Department for comment.

According to the U.S. Embassy of Kuwait website, American citizens are subject to Kuwait's laws and regulations. Those laws can "differ significantly from those in the United States," and the U.S. government may only be able to offer limited assistance to those charged, the website says.

This is a developing story. Please check back for updates.