Search Underway for Missing Mississippi Teen After Fourth of July Trip

8:32 AM PT -- A body has been found on Horn island according to Jackson County Sheriff John Ledbetter ... the identity of the body is still unknown at this time.

A massive search is underway for a Mississippi teenager who vanished during a Fourth of July trip to a popular island ... and authorities are asking anyone who spent the holiday on the water to help bring him home.

Eighteen-year-old Nolan Wells was last seen around 3 p.m. Saturday on Horn Island -- off the Mississippi coast, Ocean Springs -- according to the Jackson County Sheriff's Department. He was wearing black shorts and sunglasses when he disappeared.

Authorities say Nolan had traveled to the island by boat with friends ... but it's unclear whether he ever made it back to the mainland.

The island was packed with boaters over the holiday weekend, and officials say Wells was last seen on the island's northwest tip.

"If you were on Horn Island on July 4, traveled by boat in the area, or believe you may have seen Nolan or even given him a ride from the island, please contact authorities immediately," Gautier Mayor Casey Vaughan said in a statement posted to social media. "Even the smallest detail could make a difference."

Multiple agencies have joined the search, including the Jackson and Harrison County sheriff's departments, the U.S. Coast Guard, and the Mississippi Department of Marine Resources. The United Cajun Navy is also assisting.

Nolan reportedly is about 6 feet tall and weighs 180 pounds. He had been hanging out with a girl before he disappeared ... and his mother says her son was separated from his phone at some point before he vanished -- the device is now back with his family in Mississippi.