A New Jersey woman has been charged with child endangerment after she was found unconscious on top of her 13-month-old son, who died of apparent suffocation, authorities said.

The Burlington County prosecutor’s office said in a statement Sunday evening that police were called to a Lumberton home at about 8:30 Saturday night after a relative found Antoinette King, 33, lying unresponsive on top of her son Jerimiah, who was also unconscious.

King was dosed with the overdose-reversing drug Narcan and eventually revived, but it’s unclear whether she was overdosing. A law enforcement source said that King had appeared to be impaired or intoxicated. Joel Bewley, a spokesman for the prosecutor’s office, said his office was still investigating how King had become unconscious.

First responders were unable to revive Jerimiah; he and his mother were taken to Virtua Memorial Hospital in Mount Holly, where the boy was pronounced dead.

King has been charged with a second-degree count of endangering the welfare of a child, but the prosecutor’s office and Lumberton police are still investigating her son’s death, and the county medical examiner is expected to perform an autopsy.