PORT NECHES, TEXAS (NYTIMES) - Fears of new explosions prompted officials in south-east Texas on Wednesday (Nov 27) to order the evacuation of more than 54,000 people near a chemical plant where a powerful overnight blast left at least eight people injured.

The evacuation order covers several cities within 6.4km of the Texas Petroleum Chemical plant in Port Neches, east of Houston.

The order was expected to send thousands of people in search of shelter on the eve of one of the busiest holiday weekends.

The initial explosion at the plant shortly after midnight had sent plumes of fire skyward and rattled nearby neighbourhoods; a second blast on Wednesday afternoon launched a ball of fire high into the sky, prompting the new evacuation order on Wednesday afternoon.

The second explosion sent a tower at the plant "like a missile" toward a local high school, said Mr Jeff Branick, the judge of Jefferson County who oversees the county's Office of Emergency Management.

"The concern is that if another one were to launch - and there are a bunch left - and it were to go into the tank farm, the results would be catastrophic," Mr Branick said in an interview.

The evacuation order from Jefferson County authorities included all those living in Port Neches, along with the cities of Groves, Nederland and the northern part of Port Arthur.

The initial blast, just before 1am, happened as about 30 people were working at the plant.

Two employees and a contractor were injured, but all were later released from a hospital, company officials said.

Five residents were also injured by flying glass, according to the Office of Emergency Management.

The blast shook residents awake and turned the night sky orange with fire.

It was not clear what caused the first explosion, which happened in an area of the plant that processes a colourless gas known as butadiene used in the production of synthetic rubber and other products.

In Port Neches, a city of about 13,000, residents described the bewilderment and fear of waking up to a blast and the sight of flames.

"I thought I was dreaming," said Ms Kym Johns, 48, whose home is separated from the plant only by a street and a vacant field.

Her garage doors caved in. Sheetrock fell to the floor. A neighbour was thrown out of his chair, she said.

She and her husband, Daren, fled their home, but they returned later in the morning to pack up some things, trying to avoid breathing in the thick black smoke that was pouring out of the plant.

"Right now, I'm scared to breathe the air," she said.

Ms Regina Marple lives about a 30-minute drive from the plant, but was still shaken awake by the explosion.

"It scared me, and I jumped up," Ms Marple, 34, said. "I've never experienced an earthquake, but that's what I thought it would be like."

Her husband was working at a different plant in Port Neches at the time of the explosion, and Ms Marple did not immediately know where the explosion had occurred.

She texted him but did not hear back right away. After 15 long minutes, he called her, relieving her worst fears.

"I don't think I took a good breath until I knew he was safe," she said.

The explosion started a fire that burned unchecked into Wednesday. At about 2pm, as wind continued to blow smoke from the plant, a column collapsed, causing the second loud blast, which sent the tower hurtling into the air.

Less than an hour-and-a half later, Mr Branick extended the evacuation zone.

Earlier, officials said the fire was too dangerous to approach, so they were instead dousing equipment with water and isolating parts of the plant by cutting off a pipeline.

"I don't think the focus is really on putting the fire out; it's letting the materials that are in there burn themselves out and keeping the surrounding tanks cool," Mr Branick said at a morning news conference.

Mayor Glenn Johnson of Port Neches said he had been awakened by the blast, which damaged his home.

He lives in the area close to the plant that has been evacuated.

"I understand what getting blown out of bed means now, because you're up quick," Mr Johnson said.

The city is home to several chemical plants. Mr Johnson praised Texas Petroleum Chemical for the company's fast response and cooperation with local officials.

"They've always been very good to the city, and we appreciate them, so our hearts go out to them as well," Mr Johnson said at a news conference.

There have been several chemical explosions or fires in recent years at plants clustered in areas of oil-friendly Texas, renewing concerns about the adequacy of health and safety regulations and about environmental effects from the accidents.

Earlier this year, a disastrous fire burned for days at a petrochemical facility on the outskirts of the Houston metropolitan area.

It was followed by another blaze at a chemical plant north-east of Houston that left one person dead and two others critically injured.

A deadly explosion in 2013 at a fertiliser plant in the city of West, Texas - one of the worst industrial disasters in Texas history - was powerful enough to register as a magnitude 2.1 earthquake and nearly obliterated an entire neighbourhood.

In 2016, federal officials found that the fire had been intentionally set.

Another plant, owned by a French chemicals company, exploded in 2017 in Crosby, about 48km north-east of downtown Houston, when the city was ravaged by a tropical depression.

Ms Crystal Holmes, a spokeswoman for the Jefferson County Sheriff's Office, said that it would take time to evaluate whether the Port Neches fire was "a natural or man-made disaster".

"It looks, just visually, about half of the refinery is on fire," Ms Holmes said early on Wednesday.

Mr Monk, the chemical company's safety director, said that the large plumes of smoke from the fire might cause respiratory irritation for people nearby.

"You don't want to be downwind from this," he said.

The facility has about 175 full-time employees and 50 contractors, and spreads across 218 acres of land.

All of the employees were accounted for shortly after the explosion, Mr Monk said.

In addition to butadiene, the plant also produces raffinate, a refining byproduct used to make other chemicals.

The combined production capacity for the plant is more than 400 million kg per year, the manufacturer said on its website.

Search-and-rescue crews had gone door to door in the surrounding neighbourhood, Ms Holmes said.

Mr Jared Abshire, who lives with his family less than 1.6km from the plant, said in a Facebook message on Wednesday, "It woke us up, sounded like a train coming through the house."

Mr Abshire, 39, a production specialist at Motiva Enterprises, an oil refinery in Port Arthur, said that he and his family had evacuated their house.

Ms Marple said her husband, Mr Kristopher Marple, came home from his job at the neighbouring plant and went to sleep.

She said she was thanking God that he and the other plant workers in the city were all alive.

"It really brings home the dangers they go through every day," she said.