The multi-agency traffic stop of a light blue 1983 Thomas school bus at the Flying J in Casper on Monday led to the arrest of a California woman on felony drug charges.

Tiffanie Ammons, 44, is accused of felony possession of methamphetamine and felony possession of marijuana. She could face up to 12 years in prison and $25,000 in fines if convicted on both counts.

Ammons was arrested after a Wyoming Highway Patrol trooper stopped the school bus for failing to dim its headlights shortly before 9 p.m. Monday.

According to the affidavit, troopers approached the bus and immediately smelled marijuana when the driver opened the door.

Another trooper brought a drug dog to the scene, and the dog allegedly alerted to several bags inside the bus.

Court documents say a trooper found just less than nine ounces of marijuana in a plastic bag inside a grey and blue duffel bag. When he asked the people on the bus who the bag belonged to, Ammons allegedly claimed the bag and the marijuana.

Troopers found another 2.7 ounces of marijuana in a bag that contained Ammon's belongings, according to the affidavit, along with 3.3 grams of methamphetamine.

Patrol Lt. Chris Schell says 14 people were on the bus, headed from California to join the protest against the North Dakota Access Pipeline.

Schell believes the bus was returned to the owner, who had been driving, after Ammons was arrested. Schell says Ammons was the only person arrested, and he believes everyone else was allowed to continue their journey.