Michael Roberts, left, and Georgina Roberts face first-degree murder charges for starving their son. Jersey County Police

The father and stepmother of an Illinois boy who died of starvation last week were charged Monday with first-degree murder. The 6-year-old weighed only 17 pounds when he died, according to authorities.

Police say the boy and another child were denied food “as a form of punishment.” The parents, Michael and Georgina Roberts, both 42, were in custody Tuesday after a judge ordered a $500,000 bail on each, according to CBS News.

In addition to the first-degree murder charge, the parents faced a felony charge of child endangerment for the death and a separate misdemeanor count of child endangerment for starving their other son, who is 7.

“[The parents] knowingly and intentionally caused [the boy] to become extremely malnourished, leaving the said 6-year-old child...to starve to death,” read the criminal complaint against the Roberts.

The complaint alleged the parents starved their children on a consistent basis for the past two years and that the 6-year-old weighed about one-third of what he should have at the time of his death.

Michael Roberts brought the child to a hospital in Jerseyville, Illinois, where police were called in Friday to investigate the boy's death.

An autopsy on the child listed his cause of death as “failure to thrive due to 'extreme malnourishment',” according to KMOV. The boy who died lived with five other children, all of whom have been taken into custody by the Illinois Department of Children and Family Services.

Georgina Roberts was charged with endangering the health of a child in 2005, but the charges were dropped, KMOV reported.