Explosion at US chemical plant kills two AN explosion at a chemical factory has killed two people, injured at least 49 others and sent orange flames and huge plumes of black smoke billowing into the air in the US state of Louisiana. "We've got two dead - one confirmed dead and one missing presumed dead," said Jean Kelly, a spokeswoman for the state's department of environmental quality, which is investigating the blast. Some 600 hundred workers were inside when the blast occurred just before 9am (2300 AEST) on Thursday at the plant in Geismar, a small town north of New Orleans. Nearby residents told local media that they could feel their homes shake from the blast and some saw a huge fireball engulf part of the sprawling plant. People living within a two-mile (3.2 km) radius were told to stay inside, close their windows and shut down air conditioning units to protect themselves from the potentially toxic smoke, but the order was mostly lifted a few hours later. "We've completed our first round of monitoring," Kelly said. We didn't see any spikes of chemicals in the air. The shelter in place order was lifted for everyone except two other plants near the blast. "The fire at Williams Olefin continues to burn but is under control at this time," the Iberville Parish Council said in a midday update on its Facebook page. Please continue to monitor the situation until an all clear is given. Workers were able to close the emergency shut-down valves and isolate the unit after the blast, the plant operator said. "We are in the process of accounting for all personnel," the company said in a statement. Our emergency-response crews are thoroughly trained to respond to these types of incidents and are diligently performing their work with their first priority being the safety and well-being of people in and around the area. Louisiana Governor Bobby Jindal, who was on his way to the site to survey the damage, tweeted: "Praying for those affected by the Geismar plant explosion." The facility produces ethylene and polymer grade propylene, according to the company's website. The explosion happened two months after a blast at a Texas fertiliser plant killed 15 people - including a dozen firefighters - and injured 200 others.