ILLIOPOLIS - Investigators for the lead agency probing the April 23 explosion at the Formosa Plastics plant have not yet been able to get into the most severely damaged area because of structural instability and the possibility that dangerous chemicals are still present.

Stephen Wallace, lead investigator for the U.S. Chemical Safety and Hazard Investigation Board, estimated it will be at least the end of the month before they can get into the area where the explosion occurred.

“We have been into the peripheral areas,” he said Thursday. “We have not yet been able to get into that specific unit. There are safety concerns with the structural integrity of the building because of the damage of the explosion and residual toxic material in the area.”

Four workers were killed in the blast. A fifth died later of his injuries, and another remains hospitalized.

Rob Thibault, manager of corporate communications for Formosa, said company officials and the Occupational Safety and Health Administration are working on a plan to get investigators into the blast area. That might require shoring up the property, he said.

“We just don’t know what’s there. The concern is that there could still be some chemicals left in the piping or the reactor vessels themselves,” he said.

Wallace said he does not believe that anything done to shore up the property will harm evidence at the site. He said OSHA’s structural engineer will make sure there is a safe pathway into the area of the explosion and that OSHA will look for residual vinyl chloride to determine what safety measures investigators must take.

While they are unable to work in the blast area itself, investigators are focusing on interviewing Formosa employees and eyewitnesses and requesting paperwork from Formosa.

"We asked for drawings of the facility so we can get familiar with it, documents to help us get familiar with the production process, specific equipment, the way it operated, problems they'd had with it in the past, previous incidents," Wallace said.

"The data we get from interviews is vital, when we talk to people who are eyewitnesses who can tell us what happened that led up to it. There can be a disconnect between what's on paper and what happens in the plant, though I'm not predicting that's what happened."

Wallace estimated that the investigation may take up to a year, but if the chemical safety board is unable to get into the blast area, it could take even longer.

"Our mission is to discover the root causes of the explosion and to make recommendations," he said. "We will look for the specific cause of the explosion, the cause of the release of material and if any safety systems that did not function and what may have caused them not to function. We will look for equipment that broke and why it broke.

"We don't just want to fix the problem, but find out why it occurred."

Also, Wednesday night, two Springfield residents with a firm called Opportunity Alliance LLC made a presentation to the Logan County Regional Planning Commission asking that the panel consider expanding that county's enterprise zone to include the Formosa site.

Phil Mahler, the commission's director, said the move would allow Formosa to seek sales tax breaks on building materials and would also provide sales tax breaks on natural gas.

Thibault said Formosa hired Opportunity Alliance before the explosion in an effort to make the plant "more economically viable." He said the inquiry was related to increases in natural gas taxes on top of record high natural gas prices.

"This had been in the works for a while," he said.

Mahler said the idea was tabled because more information was needed. Logan County officials told Steve McClure and Andy Hamilton of Opportunity Alliance to check with Springfield about expanding its enterprise zone, too.

McClure said Formosa is looking at a situation now where there would be a significant amount of reinvestment, and that a sales tax break on new materials could be beneficial. Wednesday's meeting with Logan County officials was a first step in a long process, he said.

"Formosa is a multi-national corporation. We need to put our best foot forward in keeping them. In the last five years, Sangamon County has lost 21 percent of its manufacturing jobs, and that's a significant loss," he said, quoting chamber of commerce statistics.

"We're trying to help them retain those jobs, and they're committed to doing so."

Formosa is in Sangamon County, several miles south of the Logan County line.

Sarah Antonacci can be reached at 788-1529 or sarah.antonacci@sj-r.com.