Emergency response crews on Thursday remained on site, working to manage the fire caused by explosions at a chemical plant owned by TPC Group in Port Neches, about 150 kilometres east of downtown Houston, in Texas.
The company continued to work closely with the county and emergency response personnel to bring the situation under control as soon as possible and to prevent further impacts, according to a news release issued by the group.
At least 20 air monitoring stations have been established, according to the statement, but no "actionable levels" of air pollution have been reported as per state and federal guidelines.
Three people were injured early on Wednesday morning in the first blast, leading to a nearby neighbourhood being evacuated.
TPC Group said that there were 30 individuals on site when the first blast occurred and all the three injured persons were later allowed home after being treated.
The second evacuation order was issued on Wednesday after another explosion occurred. Smoke plumes resulting from the blast could be seen from as far away as 80 kilometres by late afternoon.
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The blast caused a tower to fall, but there were no reports of major injuries outside the plant.
According to TPC Group, the incident occurred in its south processing unit and involved a tank filled with finished butadiene, a chemical used in the production of synthetic rubber for tires. The cause has not yet been determined.