UPDATE 5:05pm EST: Tens of thousands of people in the area of Port Neches, Groves, Nederland, Central Gardens, Beauxart Gardens, and part of Port Arthur, Texas have been ordered to evacuate as firefighters struggle to contain a massive blaze at a chemical plant, according to an order from Jefferson County Judge Jeff Branick.

Yet more details are emerging after a massive chemical explosion at a southeast Texas refinery early Wednesday morning tore through the plant and shattered windows throughout the nearby residential area of Port Neches – about 90 miles east of Houston. Homes miles from the blast site reported windows, doors, and rooftops being shattered by the initial shock wave from the blast.

A mandatory evacuation order has been given to residents within a half mile of the burning chemical plant and so far plant operator TPC said its more than 175 full-time employees and 50 contractors are all accounted for, though a handful were transported to the hospital for burns and other injuries. At least one worker is in a serious condition.

Eyewitness accounts of the chemical explosion detailed by NBC News show a confused atmosphere when the first blast occurred at about 1am, resulting in a blaze that overtook much of the plant.

The emergency is considered “ongoing” however response crews have said that they will soon bring it under control.

One resident said:

“Their doors were blown open… doorknobs themselves were shot across rooms. We didn’t know what had exploded and what gasses were in the air,” the woman said, and described a panic scramble of nearby residents to flee the area: “I’ve never seen the traffic like that ever.”

Omar Hamza, another eyewitness described a “loud boom” and “bright flash” that was followed by an extremely loud, almost deafening explosion.

He continued:

“We waited for a little bit and we kind of looked outside and everyone was running around and freaking out. So we just grabbed the important stuff we needed — I left a note on the door and we left.”

Judge Jeff Branick of Jefferson County lives within the evacuation zone and described an almost apocalyptic scene and he initially thought they were under attack:

Branick, who lives less than a mile away from the explosion site, said his wife thought someone was shooting at their home when she heard the blast.

“I ran out with my pistol,” the judge said, before he realized it was a refinery explosion.

Texas has been the site of other major explosions, including a 2013 fertilizer plant blast in the rural town of West that killed 15 people and wiped out hundreds of homes.

It is currently unknown how much poisonous gas and chemicals has been released on the 13,000 population of Port Neches. Fires are still raging at the site.

One identified toxic chemical which scientists and emergency responders have identified is Butadiene, considered a carcinogenic substance when in contact with humans.

According to NBC:

“The refinery had butadiene, one of the constituent ingredients in synthetic rubbers, Branick said, as well as C4, a petrochemical raw material,”