NAIROBI, Kenya—A local official in northeastern Kenya says at least 10 people are dead after their vehicle ran over an explosive device on a highway Monday morning. North Eastern regional commander George Seda said the blast occurred outside Mandera town. It was not clear how many people were in the vehicle. Witnesses said the toll could rise because others had serious injuries. Police suspect the explosive device was placed by al-Shabab extremists operating in the area after crossing from nearby Somalia. The extremists are often blamed for such attacks in the border region, targeting both security forces and civilians. A police report on Monday’s blast said the attackers fled toward the border.