A religious sect believed to have been performing exorcisms is being investigated after seven people, including a pregnant woman and five of her children, were found in a mass grave in Panama.

Officials found the bodies in the indigenous region of Ngabe-Bugle, said Rafael Baloyes, senior prosecutor of the Bocas del Toro province of western Panama.

In a video published by the office of Panama’s attorney general, Baloyes said the grave came to light after locals alerted authorities at the weekend about several families being held against their will in a local indigenous-run church where exorcisms were believed to have taken place.

“We’re talking about seven victims, six minors between the ages of one and 17,” Baloyes said. “Six from one family, the mother and her five children, and the mother was pregnant.”

On Wednesday, authorities rescued 15 people being held by the religious sect. Ten sect members were arrested on suspicion of responsibility for the killings, prosecutors said.

Those rescued from the church had suffered bodily injuries, according to Alexis Munoz, a senior police official.