WELLTON, Ariz. (KYMA, KECY) - A semi-truck caught on fire Tuesday, slowing down interstate traffic. The truck was heading east on Interstate 8 (I-8), a mile from Wellton, when the fire started. KYMA spoke to the driver, who said one of the rear trailer tires ignited and spread quickly. According to the Wellton Fire Department's (WFD) Facebook post, they responded to the scene before 4:00 p.m., and upon arrival, they found "heavy fire involvement…