RIYADH, 3 July — Security authorities are investigating the discovery of an explosive device inside a US citizen’s vehicle in Riyadh on Saturday, Okaz reported yesterday. The American, who worked at King Faisal Specialist Hospital, and his spouse discovered an unfamiliar and suspicious object attached underneath the vehicle. They informed the police who removed the object, believed to be an explosive device. Okaz said the report on finding an explosive device inside the car of a British expatriate in Riyadh was false.