A massive blast at a grain elevator in northeastern Kansas killed three people and left three others unaccounted for, authorities said Sunday. Two people were hospitalized with burn injuries, said Dennis McCulloch, a spokesman for the University of Kansas Hospital. The explosion occurred around 7 p.m. Saturday at Bartlett Grain Company in Atchison, Kansas, the city’s fire department said. People three miles away felt the force of the blast, city officials said in a statement.