WARNING: Distressing content

An alleged child sex ring involving at least six children — the youngest just three years old — has been uncovered in an underground storm shelter near a home in Brent, in the southern US state of Alabama.

Prosecutors have alleged the children were drugged and tied up to a bed, a chair and a pole in the bunker.

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An official arrest indictment shows William McElroy, whose home the shelter was found near, and Dalton Terrell are charged with human trafficking and sexually abusing children in an underground bunker.

A third man, Andres Trejo, is charged with human trafficking. All three men were indicted on July 11.

A fourth person was arrested on July 22.

Timothy St. John, 23, was taken into custody for rape, sodomy, kidnapping, beastiality and animal abuse, officials said.

A Facebook post from the sheriff’s office said the investigation started in February after concerns of sexual abuse were reported.

Court documents list the children as being between the ages of three and 10 years old.

Assistant District Attorney Brian Jones described the scene inside the storm shelter: “There were chairs and beds and things of that nature and the children were drugged by Mr Trejo and tied to the bed, into the chair, into a pole. And then people would come and pay money to have sex with these children.”

Jones indicated there could be more victims and perpetrators involved in the case.

“There are some allegations with individuals that we will have a hard time identifying, just because we don’t know their names,” he said.

“And the children were drugged, according to one of the co-defendants. And so they may not be able to recognise or be able to identify anyone.”

Jones said many of the details in the case came from some of the defendants themselves.

The investigation has been challenging for authorities, who have been working on the case since the beginning of the year.

“It absolutely infuriates me but we have to kind of put that aside and just do the job. That’s all we can do,” Jones said.