A tractor-trailer carrying nacho cheese was involved in a rollover accident Sunday on Interstate-40 at the Winona Exit east of Flagstaff. DPS says the accident happened at around 10:23 a.m. and blocked the westbound lanes with the rig and cheese. The accident had westbound I-40 closed for around five hours, causing traffic to be backed up for several miles. The driver of the truck was uninjured. The cause of the accident is under investigation.