Nineteen people remain unaccounted for after a huge blast destroyed a munitions plant in central Tennessee on Friday, leaving a wide area scattered with wreckage and prompting a major multi-agency response.
Local emergency teams said the factory was operating when the blast hit, sending debris across a large area and forcing responders to wait because smaller secondary explosions continued after the first.
Officials described the scene as devastating and said families are searching for answers as teams begin a cautious investigation.
Humphreys County Sheriff Chris Davis, clearly upset during his first briefing, said several people were taken to hospital and that some had died, but he declined to give an exact toll.
"There's nothing to describe, it's gone," he said. Later in the day he confirmed 19 people were still missing and that the main explosion happened inside a big building, with debris thrown across roughly half a square mile.
Video shot from the air showed burned remains, smouldering vehicles and very little left of the factory, which is located in Bucksnort about 56 miles (90km) south-west of Nashville. The plant, sitting on around 1,300 acres, made and stored high-grade explosives such as C-4 and TNT and handled work on commercial and military munitions.
Sheriff Davis said workers who had just begun their shift "now may be missing or deceased".
Davis also warned that investigators must be careful because secondary blasts happened after the main blast and forced crews to keep their distance. "A lot of times, when I have these types of situations, I refer to them more than just a person...we're missing 19 souls," he said. He added that officers and specialist teams from federal and state agencies were on site and that the FBI and ATF had secured the area and declared it stable.
The explosion was strong enough that people in the nearby town of Waverly, about 15.5 miles (25km) away, reported feeling and hearing it.
"This was a massive enough explosion that I can tell you that folks in Waverly felt and heard this explosion," Davis said.
Some patients with minor injuries walked into local hospitals; Casey Stapp, director of media relations at TriStar Health in Dickson, said two walk-in patients were treated for "minor injuries" and released, while a third remained in care for minor wounds.
Local reports said other hospitals were also treating patients, and that residents living more than 20 miles away could feel the blast. Accurate Energetic Systems, the company that owned the site, has stopped operations, the sheriff said.
It is thought the firm employed around 75 people, and Davis said the focus now was on supporting families and employees.
State and local authorities said they were working with federal partners to respond.
Tennessee Governor Bill Lee posted on social media that his office was monitoring the situation and called it a "tragic incident". Officials said a careful and slow probe would follow, with teams remaining on scene for several days to examine what happened.
A previous blast occurred at a nearby unit in 2014 when a different operator ran that part of the plant; reports at the time said one person died and three were hurt.
Experts note that mixing explosives and filling munitions is a high-risk activity that requires well trained staff and strict controls.
Ken Cross, former president of the Institute of Explosives Engineers, told the BBC that competent workers and strong oversight are key to safety, and he said explosions are reported around the world most weeks, often in places with weaker safety rules.