ORLANDO, Fla.—The FBI and the Florida Department of Law Enforcement have joined a search that spans three counties for a missing college student who disappeared a week ago. Miya Marcano vanished on the same day a maintenance man improperly used a master key to enter her apartment, authorities said. Orange County Sheriff John Mina said Armando Caballero, a maintenance worker at the apartment complex where Marcano lived and worked, is considered the “prime suspect.” Caballero, 27, apparently killed himself; his body was found three days after Marcano was last seen. “At this time we don’t believe there was another person involved,” Mina said Thursday. The sheriff has said that Marcano had repeatedly “rebuffed” romantic advances by Caballero. Detectives spoke to Caballero after Marcano was reported missing, but had no evidence to detain him at that time. They obtained a warrant for his arrest after learning that he had entered her …