Ritch, who was autistic and nonverbal, went missing in September during a trip to Rankin Lake Park in Gastonia with his father and another unidentified adult. Ritch's body was found five days later.
An autopsy on Ritch was completed Sept. 28. The toxicology report was completed Oct. 9. ABC News obtained both reports on Nov. 29.
The toxicology report found nothing unusual in the boy's system. The autopsy found no evidence to suggest the boy was intentionally killed.
"The exam itself cannot be conclusive," the report summary reads.
The medical examiner said the findings are "not inconsistent with drowning," and "in conjunction with investigative information at this time, which gives no indication other than an accidental drowning, it seems reasonable to conclude that the likely cause of death is drowning."
On the day Maddox disappeared, his father Ian Ritch said Maddox was about 25 feet to 30 feet away before the boy broke into a sprint just as a jogger passed them.
Ian said he was a diabetic and, because he had neuropathy in his feet, he had trouble running.
"He likes running," Ian said. "I couldn't catch up with him. I feel guilty for letting him get so far ahead of me before I started running after him."
The boy's body was found on Thursday, Sept. 27, a little more than one mile from where his father had last seen him.
Family, friends prepare to say goodbye to 6-year-old Maddox Ritch
FBI uses parents' voices in search for missing 6-year-old boy in park
'This is not the end that we had hoped for:' Body believed to be missing 6-year-old Maddox Ritch found during search
'Everybody looks at you as a monster' Father of NC boy speaks for the first time since Maddox Ritch went missing
The video in the media player above is from a previous story.