​Jessica O’Daniel has not worked at the munitions plant two miles from her home for over a decade. But many of her friends and neighbors are employed at the facility, owned by Accurate Energetic Systems — an economic bedrock for families in rural Hickman and Humphreys Counties, Tenn.

Her father has a part-time job there, too, though he was off on Friday morning when an immense explosion leveled the plant, rattled homes for miles around and stunned the community. Her daughter screamed and cried as Ms. O’Daniel, 36, looked out and saw a thick, fiery plume mushrooming in the sky.

Knowing that her father was safely at home briefly calmed Ms. O’Daniel. But she quickly learned that seven of her closest friends were among the 19 people initially reported missing in the wake of the explosion. The authorities later said that one of them was found safe at home.

“It’s horrifying that they may never be found,” she said on Friday evening. “But we’re holding on to hope.”

One day after the catastrophic explosion, however, local officials said in an emotional news conference that they feared that nobody who was at the plant at the time of the blast had survived. They described a grim, volatile situation, with investigators sifting carefully through remains and potentially dangerous debris.

The F.B.I. and the Bureau of Alcohol, Tobacco, Firearms and Explosives are among the agencies investigating. Rapid D.N.A. tests are being used in the effort to find and identify remains, officials said.