Rescue teams are continuing to search the charred rubble of homes in a small Texas town for survivors of a fiery explosion at a nearby fertiliser plant.
It is feared that the explosion killed as many as 15 people, injured more than 160 and destroyed dozens of buildings.
Three to four volunteer fire-fighters were among the missing following the blast last night, said Sgt. William Patrick Swanton of the Waco, Texas, police department.
Firefighters had been fighting a fire at the West Fertilizer Co for about 20 minutes before the 8pm blast rocked West, a town of 2,700 people about 20 miles (32 km) north of Waco.
The plant had tanks of volatile anhydrous ammonia, including what initial reports said was a tanker-sized container like those hauled on freight trains.
The blast destroyed 60 to 80 houses.
It reduced a 50-unit apartment complex to what one local official called "a skeleton standing up" and left a horrific landscape of burned-out buildings and blackened rubble.
"It looks like a war zone with all the debris," McLennan County Sheriff Parnell McNamara said.
Death toll a rough estimate
Amid such devastation, the death toll remained a rough estimate of five to 15 people, Mr Swanton said.
He said more than 160 people were injured and that number was likely to rise.
Emergency crews were moving from house to house in a search and rescue operation, Mr Swanton said.
"That's good news to me, meaning that they're probably still getting injured people," he said.
"They have not gotten to the point of no return where they don't think that there's anybody still alive."
The fire-fighters had been battling the fire and evacuating nearby houses and a nursing home out of concern about possible dangerous fumes before the explosion occurred, Mr Swanton said.
Texas Public Safety Department spokesman D.L. Wilson said half the town, eight to ten blocks, had been evacuated.
Officials said 133 people were removed from the nursing home.
"There are still fire-fighters missing," Mr Swanton said.
"They were actively fighting the fire at the time the explosion occurred."
The fire-fighters were members of a large volunteer corps who had arrived on the scene.
One law enforcement official who also served as a fire-fighter was found alive but in critical condition in a local hospital, Mr Swanton said.
Cause of fire unknown
The cause of the fire remains unknown and it is being treated as a crime scene, which is standard procedure.
President Barack Obama, who flew to Boston for a memorial service for victims of the Boston Marathon bombing, offered support and prayers to the victims in Texas.
The explosion came two days before the 20th anniversary of a fire in Waco that engulfed a compound inhabited by David Koresh and his followers in the Branch Davidian sect, ending a siege by federal agents.
About 82 members of the sect and four federal agents died at Waco.
In West, witness Kevin Smith told CBS News he had just climbed the stairs to the second floor of his home when he felt the blast.
"The house exploded. It was just a bright flash and a roar, I thought it was lightning striking the house," Smith said. "I felt myself flying through the air about ten feet, and it took a second or two to realize that the roof had caved in on me so I knew it wasn't lightning."
Three hospitals in Waco and Dallas reported treating more than 160 injuries from the blast.
Ground motion from the blast registered as a magnitude 2.1 seismic tremor and created a jolt felt 80 miles(130 km) away in Dallas, the US Geological Survey reported.
The Federal Bureau of Alcohol, Tobacco, Firearms and Explosives was one of several agencies investigating.