More details are surfacing about Monday’s explosion at a military weapons factory in southeast Iowa, but many questions remain. Co-workers of the two people who are still listed as missing and presumed dead have already held memorial services for their lost colleagues, but officials at the Iowa Army Ammunition Plant have still not released their names.

Two other workers were hurt in the blast which reports now say happened in the bay housing production line one, where purple-and-white-colored plastic explosive warheads were being made. They’re called plastic because they can be molded almost like clay. That reinforced concrete bay was demolished but it had been designed to vent the force of a blast to limit damage to the rest of the factory. That apparently worked. Production at the plant near Burlington is back in operation with 800-some other employees on the job.