Scores of people are injured and an unknown number are dead after a huge explosion at a fertiliser plant near Waco in the US state of Texas.
Dozens of homes and buildings have been destroyed, and several are still on fire, after the West Fertilizer plant exploded at about 19:50 (00:50 GMT).
Some people are thought still to be trapped in buildings and a number of firefighters are reported missing.
Emergency services officials said ammonia may have caused the explosion.
It has been reported the company had 54,000lbs (20 tonnes) of anhydrous ammonia on site.
An official confirmed there were deaths, but could not give a figure.
Dean Wilson, of the Texas Department of Public Safety, told a news conference that they were still conducting house-to-house searches.
He said the fire was still smouldering and that no firefighters were tackling it as there was the risk of further explosions.
Half the town had been evacuated, he added.
The Waco Tribune-Herald reported that firefighters had been trying to put out a fire at the plant when the explosion happened, and that some were among those injured.
The blast happened in West, a town of about 2,700 people some 20 miles (32km) north of Waco.
TV images showed streams of emergency vehicles descending on the site and ambulance crews using a nearby sports field as an emergency treatment area.
Glenn A Robinson, chief executive of Hillcrest Baptist Medical Center in Waco, told CNN that his hospital had received 66 injured people including 38 who were seriously hurt.
He said the hospital was seeing "everything from orthopaedic injuries to patients that are experiencing serious blood loss".
McLennan County Sheriff Parnell McNamara said: "It's a lot of devastation. I've never seen anything like this. It looks like a war zone with all the debris."
Unconfirmed reports said a nursing home had collapsed in the explosion and some people were believed trapped inside.
Witness Debby Marak told the Associated Press news agency that she had seen smoke coming from the area near the plant and had driven over to see what was happening.
She said that when she arrived, two boys ran towards her screaming that the authorities had told them to leave because the fertiliser plant was going to explode.
She said she drove a short distance before the blast happened.
"It was like being in a tornado," she said. "Stuff was flying everywhere. It blew out my windshield. It was like the whole earth shook."
Another resident told KWTX-TV that she heard several explosions from 13 miles (20km) away.
"It sounded like three bombs going off very close to us,'' said Lydia Zimmerman.
Texas Governor Rick Perry said in a statement: "We are monitoring developments and gathering information as details continue to emerge about this incident.
"We have also mobilised state resources to help local authorities. Our thoughts and prayers are with the people of West, and the first responders on the scene."
The Dallas Morning News reported that West Fertilizer had told the Environmental Protection Agency that it presented no risk of fire or explosion.
The newspaper said it had seen documents in which the plant said it stored large amounts of anhydrous ammonia, but the worst scenario envisaged was a release of ammonia gas that would harm no-one.