The scope of the explosion that devastated a large part of this quiet central Texas town became clearer Thursday as search teams scoured damaged and collapsed buildings for survivors and those who perished when a tank reportedly containing liquid ammonia exploded at a local fertilizer business.

Officials at one point put the death toll as high as 15, but later in the day backed away from any estimate.

Several family members and organizations confirmed that as many as eight emergency workers, five of them West volunteer firefighters, were among the dead or missing.

The blast shook the ground with the strength of a small earthquake and crumpled dozens of homes, an apartment complex, a school and a nursing home. Its dull boom could be heard dozens of miles away from the town about 20 miles north of Waco. There was no indication the blast, which sent up a mushroom-shaped plume of smoke and left behind a crater, was anything other than an industrial accident touched off by a fire.

More than 160 people in the town of about 2,800 were injured in the Wednesday night explosion, which damaged structures more than a mile away and rained burning embers and debris down on terrified residents. The landscape Thursday was wrapped in acrid smoke and strewn with the shattered remains of buildings, furniture and personal belongings.

Daylight revealed areas that looked like they had been pounded by artillery, leaving acres of collapsed roofs and buildings, twisted trees and railroad tracks, and demolished vehicles.

A 15-unit apartment complex less than 1,000 feet from the family-run West Fertilizer Co. was heavily damaged.

“A significant area around the fertilizer plant … has been destroyed. Homes have been destroyed. There are homes flattened. Part of that community is gone,” said Sgt. William Patrick Swanton, a Waco police spokesman who is helping the town with communications.

West Mayor Tommy Muska said 50 to 60 homes were damaged within five blocks of the blast.

Swanton said volunteer firefighter and a constable were at the scene fighting a fire when the plant exploded.

Several of the volunteer firefighters who responded to the initial fire were unaccounted for Thursday, Swanton said.

“There are some true heroes out there today,” Swanton said. “And they are civilians.”

President Barack Obama said Thursday: “Today our prayers go out to the people of West, Texas, in the aftermath of last night’s deadly explosion at a fertilizer plant. A tight-knit community has been shaken, and good, hard-working people have lost their lives.”

The family of 47-year-old firefighter Morris Bridges was told Thursday that he was among the missing, said his son, Brent Bridges, 18.

The Dallas Fire-Rescue department said that one of its off-duty fire captains, Kenny Harris, 52, a resident of West, was killed in the explosion. A married father of three grown sons, Harris wasn’t on duty when he decided to lend a hand to volunteer firefighters battling the fire.

Perry Calvin, a resident of Emmett, 35 miles northeast of West, was attending an emergency medical technician class in the town with a friend when they responded to the fire alarm at the fertilizer distribution center.

“They just went to help fight the fire,” said Calvin’s father, Phil, who is chief of the Navarro Mills Fire Department. Phil Calvin said he learned Thursday afternoon that both his son and his friend were among the dead.

Injured people were treated on West’s floodlit high school football field, until a second tank at the fertilizer company was recognized as a hazard. After that, people were told to leave the area immediately.

Waco’s Hillcrest Baptist Medical Center said it had treated more than 100 people hurt in the blast. Burn victims and others were taken to hospitals as far away as Dallas and Fort Worth, more than 70 miles to the north. Three elderly patients were admitted to John Peter Smith Hospital in Fort Worth.

Some structures, including the apartment building, had to be reinforced before search crews could safely enter, Swanton said.

Gary Adair, whose father owns the decades-old fertilizer business, said it had been closed for about three hours when the explosion occurred. The family had no idea what caused it, he said.

“Everybody in town basically knows everybody,” the son said, sobbing. “It’s really rough. It’s a tragedy.”

Though he was awaiting confirmation like the rest of the town, Adair said he had a pretty good idea of who was among the dead.

“There are people you know just like a brother,” he said.