GEISMAR, Louisiana (CNN) -- A second man has died as a result of Thursday's explosion at a Louisiana chemical plant, the Louisiana State Police said Friday.
Scott Thrower, 47, of St. Amant, died at a Baton Rouge hospital after suffering burns in the blast at the Williams plant in Geismar, state police trooper Jared Sandifer said.
The Thursday morning explosion killed one other worker and injured more than 100 others in what company CEO Alan Armstrong characterized Friday as "a terrible and unprecedented tragedy and an extremely difficult time for all of us."
Before Thrower's death was announced, the company said six people -- two employees and four contractors -- still were hospitalized Friday. Their conditions weren't available.
The explosion at the plant, which Williams says produces about 1.3 billion pounds of ethylene and 90 million pounds of polymer-grade propylene each year, sent a plume of thick smoke into the air and initially forced authorities to ask people nearby to stay inside to avoid exposure to potentially toxic fumes.
Investigators still were waiting for the plant to be safe enough to investigate the blast's cause, officials said Friday.
Armstrong told reporters Friday that the incident was tough to take.
"A lot of us in this industry have spent much of our careers working to make it safe to operate, so when something happens like this, honestly it feels like a big failure," Armstrong said. "I would tell you we're very committed to returning to a safe operation, but this industry works extremely hard to make these operations safe, so it's very, very disheartening when something like this occurs."
A dramatic image provided to CNN affiliate WAFB by a plant worker who did not want to be identified showed workers running from a towering orange column of flame ripping through part of the plant on Thursday. The fire has since been extinguished.
The plant had a minor propylene leak Friday, but the chemical vaporized as it came out, Sandifer said. The state Department of Environmental Quality and Williams-hired air monitoring contractors are checking the site, and air-quality tests so far have found nothing concerning, he said.
"There is no threat to the public of any toxic chemicals being in the air," Sandifer said.
Authorities lifted a shelter-in-place order for people in the area Thursday afternoon.
Three employees and 100 contractors received medical treatment after the blast. More than 830 people were at the site -- more than usual, because of a plant-expansion project, plant manager Larry Bayer said Friday.
Bayer said the blast happened in the plant's propylene fractionation area, but said he didn't know what led to the explosion.
"We have been waiting for the last amounts of residual hydrocarbons to escape from the ... piping through the night. An investigation to determine what happened is still pending and will begin as soon as our team is allowed to go back into the plant by the state police," Bayer said.
About 25 workers were in the facility's control room Friday to monitor the situation, but the plant has effectively shut down, company officials said.
The first worker who died, killed 29-year-old Williams employee Zachary Green, joined the company in October. Williams officials met with his family at their home Thursday, the company said.
"We are grieving for the loss of Zack, who was part of our Williams community," Armstrong said in statement Thursday. "Our thoughts and prayers are with the family at this time of sorrow."