Islamic State group leader Abu Bakr Baghdadi is reportedly sick after he and three other terrorist commanders were recently poisoned. They were taken to an unknown location to keep them safe, Russian site Sputnik News reported Monday.

The trio, including top ringleader Baghdadi, were poisoned together at a location in the southwest sector of Mosul, Iraq, just near the Syrian border. Militants with the group also known as ISIS have started arresting people to find out who is responsible, an unnamed source told the Iraqi Media News Agency.

It is currently unknown how the four commanders were poisoned or with what, except that the toxin was prepared in some sort of meal. The identities of the three other commanders is also presently unknown.

Baghdadi is responsible for turning ISIS into a formidable force in northern Iraq and parts of Syria after helping the group splinter off from al-Qaeda. Over the last three years, ISIS has flourished under his leadership, taking key parts of Iraq and Syria. More recently, ISIS has been under attack from the Iraqi Security Force and United States-led airstrikes that have weakened the militant group's reach in the region.

Last month, reports indicated Baghdadi was pinned down and hiding somewhere in Mosul, after two years of speculation over whether he was killed in the same city in the summer of 2014, according to Express. Baghdadi was eventually spotted leaving his hideout to deal with riots that had rocked the city.

Baghdadi is believed to be 45 years old and from Samarra, located north of Baghdad. Some reports have indicated he may have been a cleric at a mosque there before helping ISIS to form its so-called caliphate in Iraq and Syria, but little’s been confirmed of his past.

He made his first public appearance on camera in July 2014, according to BBC News. At one point, the U.S. offered up a $10 million reward to anyone who could provide information resulting in his capture or death.