Naya Rivera's autopsy is now complete and officials confirm she died by drowning.

According to the Ventura County Medical Examiner's Office ... they had to confirm Naya's identity using dental records. The cause of death is listed as drowning and the manner of death is an accident.

Officials say the autopsy findings are consistent with a drowning and the condition of the body is consistent with the time that she was submerged. They also said, "There is no indication from the investigation or examination that drugs or alcohol played a role in the decedent's death, but specimens will be submitted for toxicology testing."

TMZ broke the story ... the "Glee" star's body was recovered from Lake Piru Monday. Ventura County Sheriff Bill Ayub's said there was nothing to indicate any foul play took place or that she died by suicide. Sadly, he said this was simply a tragic accidental drowning death.

Naya's body was discovered in the northeast portion of the lake, near the surface of the water. The sheriff also said that, based on conversations with Naya's 4-year-old son, Josey Hollis Dorsey, the 2 of them went out for a swim. But, while she was able to boost him back on the boat ... she had disappeared below the surface.

The current was, apparently, very strong the day Naya went missing. Ayub said that may have contributed to her drowning. Also, the boat Naya and her son had rented that day was not anchored when they went for a swim.

As we reported ... Naya was reported missing last week. She was later presumed dead as the search shifted from a rescue to a recovery mission. She was 33.