Kehoe had free access to the school building during the summer vacation of 1926. From mid-1926, he began buying more than a ton of pyrotol, an incendiary explosive used by farmers during the era for excavation and burning debris. In November 1926, he drove to Lansing and bought two boxes of dynamite at a sporting goods store. Dynamite was also commonly used on farms, so his purchase of small amounts of explosives at different stores and on different dates did not raise any suspicions. Neighbors reported hearing explosions set off on the farm, with one calling him "the dynamite farmer". Following the disaster it was reported that Michigan State Police investigators had discovered that a considerable amount of dynamite had been stolen from a bridge construction site and that Andrew Kehoe was suspected of the theft. Investigators also recovered a container of gasoline in the school's basement. The container was rigged with a tube and investigators speculated that Kehoe had planned that the gasoline fumes would ignite from a spark scattering burning gasoline throughout the basement. In the undamaged section of the school it was found that Kehoe had concealed the explosives in six lengths of eavestrough pipe, three bamboo fishing rods and what were described as "windmill rods" that were placed in the basement ceiling.