Los Angeles County sheriff’s deputies and family members are searching for a missing teenager.

Jonas Nelson, 19, was last seen by his father Wayne Nelson on Chaney Traill in Altadena at around dusk on Jan. 7.

The 6-4,190-pound teen was last seen wearing an orange jacket with silver stripes. Jonas — who, according to his father, has been on that trail many times and likes to hike alone — went around the locked bar blocking the road at the beginning of the mountainous area while his father was putting a leash on the family dog. Jonas was out of sight by the time the elder Nelson got out of his truck and walked to the popular hiking spot.

According to his father, Jonas is suffering from undiagnosed mental illness caused by an undisclosed drug-related incident.

Jonas had stopped taking his medication because it made him sick. Still, his father says Jonas was in complete control of his faculties when they arrived together at the entrance to the trail.

“He said he was going to stop smoking [marijuana] and get back in school. He wanted to play basketball again. We were heading to 24-Hour Fitness after we went to Chaney Trail. He was healing his mind,” said the father.

Wayne came back to his truck after he saw a sheriff’s deputy approaching the vehicle, which was in a no-parking area. He waited there for Jonas, but still was not worried. The father later left to pick up some food on nearby North Lake Avenue, then returned to the area before heading to his mother Irene’s home, located a few blocks away from the popular hiking spot.

“I thought he went there,” Wayne said. “He has done that before. I went back to the trail and called his name and looked for him.”

Wayne said he has called Jonas’s cell phone several times. The son has not been active on any of his social media accounts since he disappeared.

Sheriff’s deputies have checked the area twice with a search and rescue team, and Wayne rushed to McDonald’s on Lincoln Avenue several days ago after someone misidentified a teenager as Jonas.

“I just want to hear something from him,” Wayne said. “If he’s reading this, I want you to text me and give me some kind of sign that you’re OK.”

Anyone with information about Jonas’s whereabouts are asked to call (626) 360-9820, (626) 712-4908, (626) 905-9505 or (626) 584-1500, ext. 114.