A powerful explosion that tore through a central Tennessee ammunition plant on Friday morning has left 19 people missing, putting the small rural communities surrounding the facility on edge.

The authorities were still reaching out to affected families and said the investigation was still in progress as of Friday evening. Officials said several people had died in the explosion but did not specify how many.

“Anytime you have a situation like this, there’s grief involved,” said Sheriff Chris Davis of Humphreys County, Tenn., describing the conversations he’d had with some of the families of the missing. The situation is “hell,” he added.

Here’s what we know about the blast.

When and where did it happen?

The explosion occurred at 7:45 a.m. Central time at a plant owned by Accurate Energetic Systems, which produces explosives and demolition charges for the U.S. military.

The facility is roughly 60 miles southwest of Nashville on a sprawling 1,300-acre campus straddling Hickman and Humphreys Counties in rural Tennessee.

Witnesses said the explosion was so powerful that it rattled homes at least a dozen miles away and generated a plume of smoke large enough to show up on the weather radar of a Nashville television station.