A 19-year-old Arizona man who was questioned as a person of interest in the Phoenix area's spate of highway shootings is not the prime suspect and the investigation continues, authorities said on Saturday.

State troopers detained Oscar De La Torre Munoz, of Avondale, Arizona, on Friday at a Phoenix-area gas station along with a woman who was later released. He appeared in court on an unrelated marijuana possession charge on Saturday.

Bart Graves, a spokesman for the state's department of public safety, said De La Torre Munoz is not considered the prime suspect by authorities probing 11 possible vehicle shootings since Aug. 29 on a roughly 10-mile (16-km) stretch of Interstate 10 where it runs through the Phoenix metro area.

Graves said the investigation is ongoing.

The head of Arizona's state police has described the incidents on the interstate, the southernmost transcontinental highway in the United States, as "domestic terrorism."

In a brief appearance before a judge at around 5 a.m. local time, De La Torre Munoz confirmed his name and date of birth, and was read the marijuana possession charge.

In video of his arrival a day earlier at the Fourth Avenue Jail in downtown Phoenix from local news channel ABC15, De La Torre Munoz was asked by a reporter whether he was involved in the shootings, or if he knew anything about them.

"No," he replied as he was led into the building.

In the latest confirmed incident, a driver discovered a bullet hole in the side of his commercial truck on Thursday.

Only one person has been injured: a 13-year-old girl suffered a slight cut to her ear when the windshield of the sports utility vehicle she was in shattered during the first shooting on Aug. 29.

Of the 11 incidents under investigation, police say eight involved gunfire, and the others some sort of projectile. Authorities have offered a $20,000 reward for information leading to an arrest and conviction in the case.