A Utah school bus driver was arrested this morning on suspicion of DUI after other drivers as well as her passengers called 911 to report erratic behavior.

"Whoever is driving this thing can't maintain a lane," a male caller said.

Authorities allege that Lycia Martinez, 39, was driving under the influence of as many as four prescription medications.

"They were prescription medications prescribed to her," Trooper Blaine Robbins told ABC News affiliate Good4Utah.com. "On all the pill bottles, they do say they can cause drowsiness, dizziness, things of that nature. … They were in her purse."

Authorities said the Davis County School District bus was traveling a Utah highway with nearly 80 elementary school children and adults out on a field trip.

From the bus, a chaperone told a 911 dispatcher that passengers were "concerned."

"It is freaking scary," another caller said.

"She can't stay in the lanes," the chaperone said. "She's crossing the double lines and the adults are getting scared. … She almost hit a van next to us."

Martinez was given a field sobriety test, arrested and then taken to jail. Martinez doesn't have a listed phone number, and it's unclear if she has an attorney yet, the Associated Press reported.