The United States hit a gold mine of important information on the Islamic State (ISIS)' operations when U.S. commandos captured the terror group's chemical and biological weapons expert last month.

Now, the ISIS detainee identified by a senior defence official to NBC News as Sleiman Daoud al-Afari is giving American authorities important details on how the jihadist organisation operate and secure their weapons.

"He's a bad guy," the unnamed defence official said to describe al-Afari, who also formerly worked for the regime of Iraqi ruler Saddam Hussein.

After being interrogated by U.S. military officials, the captured Islamic militant is expected to be turned over to Kurdish forces by the end of this week.

Al-Afari is said to be the first Islamic militant to be captured by the U.S. military's special operations forces.

The force is comprised of two separate 50-man units of U.S. special operations forces specifically targeting top ISIS officials in both Iraq and Syria known as "Expeditionary Targeting Force."

These units, formed in December last year, are also responsible for gathering intelligence from the terrorist group, and freeing its hostages.

The unnamed military source further believes the ISIS detainee is also responsible for some of the terror group's deadly operations.

One possible attack masterminded by al-Afari is the ISIS operation in August last year that involved the use of an outlawed chemical agent outside Aleppo, Syria, likely killing a baby.