Pilot and passenger arrested on drug charges after plane makes emergency landing in California.

A small plane made an emergency landing on a Southern California highway — and the flight instructor and his student pilot were arrested on drug smuggling charges, according to police.

The pilot, 21-year-old Gabriel Leon Breit, called authorities around 1:45 a.m. Thursday morning and reported that the Piper Cherokee Pathfinder had engine trouble and he was landing on State Route 76 in Oceanside, NBC San Diego reported.

Breit and his passenger, 36-year-old Troy Othneil Smith, were uninjured and landed the boat safely – but when police arrived, they saw one of the men hiding a backpack in roadside bushes, Oceanside Police Deputy Chief Taurino said Valdovinos at a press conference.

Breit, a flight instructor, and Smith, his student, were arrested.

Police discovered a small amount of cocaine on Smith. Another kilo of cocaine was discovered in the backpack. Both were accused of drug trafficking.

“It doesn't surprise me. I think drugs enter our country in different ways, but I think the surprising thing is the emergency landing and how we encountered it,” Valdovinos told reporters.

Investigators said the plane left Oceanside Wednesday afternoon and made a brief stop in the Phoenix area. Later that night it was on its way back to Oceanside when it had to land on the road.

The plane's owner told NBC San Diego that he rents the plane through a flying club called Plus One Flyers, which requires a private pilot's license and a high-performance aircraft permit to charter his plane.

Plus One confirmed that Breit and Smith rented the aircraft as flight instructors and student pilots, respectively.

The owner, who wished to remain anonymous, said he was alerted to the emergency landing around 6:30 a.m. and later learned of the drug bust from the news.

“You just can’t write something like that,” said the owner. “Unbelievable. Unbelievable that people would do something like that.”

Breit's grandfather, Victor Keisman, told the medium that it “makes no sense that he would get in trouble.”

“He worked his hours hard because for the FAA [pilots] “I need at least 1,500 hours to become a commercial jet pilot and he said he would get it by the end of this year,” the grandfather added.

Keisman said he flew with his grandson several times.

“He's very professional, so it doesn't suit his character. I have no idea what happened. I have no idea.”

The Drug Enforcement Administration said it was working with Oceanside police and confirmed it served a search warrant Thursday morning.

The plane was in transit for nearly half a day for the investigation, which was handled by the North County Narcotics Task Force.

The Federal Aviation Administration is investigating the circumstances of the emergency landing.

Breit and Smith were both released on bail Thursday evening.