A 53-year-old Montana man reported missing last week was found dead Tuesday morning in his submerged vehicle in the Snake River near Massacre Rocks, authorities said.

Kee Ray Begay Jr. of Montana was discovered at approximately 8:30 a.m. Tuesday morning after an extensive search effort using advanced technology that included sonar equipment and both aerial and underwater drones, Power County Sheriff Josh Campbell told the Idaho State Journal Tuesday evening. His body was recovered from the water around 3 p.m, the sheriff said.

The Power County Sheriff’s Office shared a a missing person alert from the Gallatin County, Montana, Sheriff’s Office for Begay on Dec. 28 after his cellphone was pinged to Interstate 86 westbound in the Massacre Rocks area. He had last spoken to his wife on Dec. 21, nine days before he was found.

Begay was driving a black 2014 Dodge Avenger with Arizona license plates.

Campbell said his team began searching the area where Begay’s phone had last pinged on Monday.

“Yesterday, my chief deputy, deputies and I went out to the last known area, did some research, and found out that there were multiple pings in that area,” Campbell said.

The search team deployed multiple technologies to locate Begay. They used an aerial drone equipped with FLIR (Forward-Looking Infrared) thermal imaging capabilities and a jet ski equipped with side-scan sonar.

“We used our jet ski with sonar, got a blip and contacted our search and rescue team,” Campbell said.

Power County also called in the Bingham County Search and Rescue team, which has an underwater drone, ultimately locating the Avenger with Begay’s body inside, Campbell said.

“With side-scan sonar, we found what we believed to be a vehicle at about 8:30 a.m.,” Campbell said. “We waited for the rest of the team to get there, and we were able to get the vehicle and the individual out of the water around 3 p.m.”

Campbell said the initial investigation suggests the death was accidental.

“There isn’t anything other than it was an accident, nothing suspicious, at this time,” Campbell said. “The case is still under investigation. We’re not going to release a whole lot of detail, but we’re still investigating all avenues, trying to determine exactly what happened.”

The sheriff said his office will release additional information once the investigation is concluded.

The search effort involved coordination between the Power County Sheriff’s Office and Search and Rescue, Bingham County Search and Rescue and the Gallatin County, Montana, Sheriff’s Office.