Nolan Wells' death has been determined to be "consistent with a drowning" ... months after the 18-year-old vanished during a Fourth of July boating trip to Mississippi's Horn Island.

According to the Mississippi State Medical Examiner's autopsy report, Nolan's manner of death was ruled "undetermined."

“The Grand Jury finds that the position of, the condition of, time of discovery, and location of Mr. Wells’ body is consistent with drowning,” the report read. The Grand Jury, which consisted of 13 men and 10 women, was impaneled on April 20, per local reports. They met again on September 14 and ended on September 18. The report also noted Nolan did not have cocaine in his system, despite rumors.

The report noted that bruising was found on the back of Nolan’s head … but it was not considered a fatal injury. 

Jackson County District Attorney Angel Myers McIlrath revealed the grand jury came back with a "no true bill" ... meaning they did not find anybody was responsible for Nolan's death.

The D.A. released a video in which she said there was "absolutely no evidence" to support the claim that Nolan’s death was “racially motivated.”

"The death of Nolan Wells has devastated our community. Outsiders and influencers have attempted to exploit Nolan’s death to divide and create chaos here, but we are better," the D.A. added.

Edward Andrew Paltzik, an attorney for Nolan's friends, tells TMZ, "NO TRUE BILL."

He continued, "We said it all along: Warren Hudson, Jax Pitalo, and Morgan Seymour were always completely innocent. There was never any doubt. They are terrific people."

The state conducted Nolan's autopsy July 7 -- one day after his body was found along the Horn Island shoreline -- but the findings remained under wraps for weeks.

As we reported ... Nolan traveled to the island with friends on July 4 but never made it back to the mainland. His friends said they tried to convince him to leave around 4:30 PM, but he refused.

Nolan was reported missing that night ... and his body was discovered two days later, near where he was last seen alive.

Authorities initially believed Nolan drowned and said they had found no evidence of a crime ... but his family repeatedly questioned that explanation and launched its own investigation.

The family hired attorney Ben Crump and arranged an independent autopsy, which found a large area of red discoloration at the back of Nolan's head ... a finding the examiner said could indicate an injury.

However, the independent examiner listed both Nolan's cause and manner of death as undetermined pending further investigation.

Crump said the examiner did not receive all of Nolan's organs -- including his throat and lungs -- or the autopsy photos needed to help determine the circumstances when he entered the water.

Crump's team also hired audio experts to review the full Sea Tow call placed after one of the group's boats began taking on water ... along with oceanic engineering experts to study the tides and the location where Nolan's body was found.

The United Cajun Navy later compiled a separate report using photos, videos, coordinates and witness material. The group said Nolan's last sighting was sometime between 3:23 and 4:27 PM -- leaving a major gap in the timeline before the boat he arrived on departed at 4:31 PM.

Nolan's family has maintained they will continue pressing for answers about what happened during his final hours.