ISIS is forming a “chemical weapons cell” made up of countless experts from Iraq and Syria, a report says.

A US official told CNN that the terror group is gathering all of its chemical weapons specialists from across the Middle East and bringing them to their new “de facto” capital in the Euphrates River Valley.

Located in Syria, between Mayadin and al Qaim, the cell will sit just across the Iraqi border — and will be composed of people who’ve never worked together.

A defense official told CNN that “thousands” of ISIS operatives and sympathizers are believed to be in the area, and that Islamic State leader Abu Bakr al Baghdadi may also be hunkered down there.

The region has served as headquarters for the group in the wake of the US-led offensive on Raqqa, its one-time capital.

“We know they have been moving a lot of their leadership out of Raqqa and we suspect much of their technical expertise and planning as well,” explained US Maj. Adrian Rankine-Galloway, a Pentagon spokesman.

ISIS has unleashed more than 15 chemical weapons attacks since April 14 in or around west Mosul, according to military officials.

There have been no US or coalition casualties, but Iraqi troops reportedly have been treated for injuries.

Experts ultimately fear that an advancement in chemical warfare could make things a lot worse in the Middle East.

“We know ISIS is willing to use chemical weapons,” Col. Ryan Dillon, a spokesman for the US-led military coalition, told CNN.

“We have seen ISIS use low-grade chemical agents in the past,” he said. “This is not something we want to see them get good at.”