Two employees and one contractor were injured in the initial blast at 1 a.m., but all were treated and released from hospitals, officials said.
The EPA reports that TPC has been among the "high priority violators" every quarter since Jan. 2017, with additional violations dating back to at least 2004. TPC has paid at least $180,000 in fines in the past 5 years.
TPC also received a penalty for an OSHA violation. According to OSHA, they received a $11,224 penalty for a serious violation on Nov. 1, 2016. TPC was cited for "safeguards for personnel protection." It appears there was an informal settlement and the penalty was reduced to $6,735. The company was also cited for "selection and use of work practices."
The Texas Commission on Environmental Quality says the incident is causing the release of chemicals called volatile organic compounds (VOCs). Elevated levels of VOCs from this facility are odorous. Short-term exposure to high concentrations of VOCs can cause eye, nose, and throat irritation, shortness of breath, headaches, and nausea. If you experience these health effects, leave the area until the situation has resolved.
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By early Wednesday afternoon, another blast rocked the plant as personnel continued to fight the fires on site. That explosion was caused by the collapse of a flaring tower, according to Jefferson County Emergency Management Coordinator Michael White.
More flaring towers could also fall as the response continued, White said.
Black debris was seen floating in the air hours after the initial blast, as crews continued to spray water onto the impacted areas of the facility. Residents were advised not to touch the floating debris with their bare hands.
"The black stuff floating, don't touch it," said Troy Monk, who is the director of health safety and security for the TPC Group.
The smoke plume from Port Neches could be seen from as far away as 50 miles by late afternoon.
Windows were shattered and a number of structures were damaged from the initial blast, according to posts on social media.
WATCH: 3 injured by plant explosion in Port Neches
TPC said the injured workers were all transported to hospitals and were treated and released. One worker suffered a broken arm. Another was flown to Memorial Hermann-Texas Medical Center after they inhaled hot air, White said.
Jefferson County Judge Jeff Branick says there are no reports of major injuries to people outside the plant.
Everyone working in the plant was accounted for. There were as many as 27 people on site when the explosion happened, according to officials.
RELATED: People living within four miles of the plant were ordered to evacuate.
WATCH: Residents recount feeling the explosion rock their homes
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