Up to 15 people have been killed in an explosion at a fertiliser plant in Texas, police said today.

Between five and 15 people died and more than 160 were injured in the blast at West Fertiliser in the town of West, 80 miles south of Dallas, officials said.

The explosion left the factory a smouldering ruin and levelled buildings for blocks in every direction, and was heard as far as 45 miles away.

It sent flames shooting high into the night sky, and rained burning embers, shrapnel and debris down on shocked and frightened residents.

A member of the city council, Al Vanek, said a four-block area around the explosion was "totally decimated".

Other witnesses compared the scene to that of the 1995 Oklahoma City bombing. Authorities said the plant made materials similar to that used to fuel the bomb that tore apart that city's Murrah Federal Building.

Waco police Sergeant William Patrick Swanton said the death toll is only an estimate as search and rescue operations continue.

The explosion shook the ground with the strength of a small earthquake in the community of 2,800 people about 20 miles north of Waco.

Sgt Swanton said there is no indication the blast was anything other than an industrial accident.

The mayor of West, Tommy Muska, told reporters the town needs "your prayers".

"We've got a lot of people who are hurt, and there's a lot of people, I'm sure, who aren't gonna be here tomorrow," Mr Muska said last night. "We're going to search for everybody. We're going to make sure everybody's accounted for. That's the most important thing right now."

Dozens of emergency vehicles amassed at the scene in the hours after the blast, as fires continued to smoulder in the ruins of the plant and in several surrounding buildings. Aerial footage showed injured people being treated on the flood-lit sports field that had been turned into a staging area.

Mr Vanek said first-responders treated victims at about half a dozen sites, and he saw several injured residents from the nursing home being treated at the community centre.

Sgt Swanton said this morning the injured were being taken to hospitals in Waco and a triage centre at a high school in nearby Abbott.

Mr Muska, who is also a volunteer firefighter, said the town's fire department went to the plant to fight a blaze at about 6.30pm, and the blast that followed knocked off his fire helmet and blew out the doors and windows of his home nearby.

Five or six volunteer firefighters were at the plant fire when the explosion happened, Mr Muska said, and not all have been accounted for.

Among the damaged buildings were 50 to 75 houses, an apartment complex with about 50 units that was reduced to "a skeleton", a middle school and West Rest Haven Nursing Home, from which first-responders evacuated 133 patients, some in wheelchairs.

Erick Perez, 21, of West, was playing basketball at a nearby school when the fire started. He and his friends thought nothing of it at first, but about a half hour later, the smoke changed colour. The blast threw him, his nephew and others to the ground, and showered the area with hot embers, shrapnel and debris.

"The explosion was like nothing I've ever seen before," Mr Perez said. "This town is hurt really bad."

Texas governor Rick Perry said state officials were waiting for details about the extent of the damage.

"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."

Resident Debby Marak said she noticed a lot of smoke in the area across town near the plant, and drove over to see what was happening, and that when she got there, two boys came running toward her screaming that the authorities had ordered everyone out because the plant was going to explode.

She said she had driven only about a block when the blast happened.

"It was like being in a tornado," the 58-year-old said. "Stuff was flying everywhere. It blew out my windshield. It was like the whole earth shook."

Sgt Swanton said he had no details on the number of people who work at the plant, which was cited by the Texas Commission on Environmental Quality in 2006 for failing to obtain or to qualify for a permit. The agency acted after receiving a complaint in June that year of a strong ammonia smell.

Among those believed to have been killed are a group of volunteer firefighters and a police officer who responded to the fire call about an hour before the blast. They remain unaccounted for.

The town's volunteer firefighters responded to a call at the plant at 7.29pm, Sgt Swanton said, adding that, due to the plant's chemical stockpile, "they realised the seriousness of what they had".

The main fire after the blast was under control by 11pm, but residents were urged to remain indoors because of the threat of new explosions or leaks of ammonia from the plant's ruins.

In the hours after the blast, many of the town's residents wandered the dark streets searching for shelter. Among them was Julie Zahirniako, who said she and her son Anthony had been playing at a school playground near the plant when the explosion hit.

The explosion threw her son 4ft in the air, breaking his ribs. She said she saw people running from the nursing home and the roof of the school lifted into the air.

"The fire was so high," she said. "It was just as loud as it could be. The ground and everything was shaking."