MASCOUTAH, Ill. -- The source of an irritant that sent three workers in a southwestern Illinois air base's mail center to the hospital may forever be a mystery, authorities said Thursday.
Lt. Benjamin Garland said a "thorough and exhaustive examination" by bio-environmental specialists was unable to determine what caused Wednesday's illnesses at Scott Air Force Base and a brief evacuation of that portion of the installation.
"We're really grateful we came to a safe resolution of this incident," Garland said.
Officials have said it's possible whatever caused the mail handlers to develop respiratory or skin reactions and spurred the precautionary decontamination of 13 other people who had been at the scene may have dissipated by the time tests were done later in the day.
"There was definitely unmistakable evidence of symptoms of an irritant," though no source of it could be uncovered after several packages were scrutinized, Garland said. "At this point, it's going to be a mystery."
The mail center remained closed Thursday, though an education center and other services housed in that building were reopened later Wednesday at Scott, near the town of Mascoutah about 25 miles east of St. Louis.
The base's commander, Col. Michael Hornitschek, said he didn't believe there was ever any threat to the local community and that it's possible the package could have been a "very benign shipment someone had sent (and that) something had spilled or broke." But he stopped short of assuring that it wasn't a deliberate act.
Hornitschek said he believed the matter was "absolutely not" connected to the pending 10th anniversary of the Sept. 11, 2001, terrorist attacks -- a sentiment Garland again stressed Thursday.
"There's no evidence that it's related to 9/11 or a terrorist attack of any sort," Garland said. On the base where there are 10,000 to 12,000 people any given day, "our personnel are currently safe, and the buildings in which they work have been declared safe."
The air base serves as a global mobility and transportation hub for the Defense Department. The base is home to the U.S. Transportation Command, Air Mobility Command, the 618th Air and Space Operations Center and Air Force Network Integration Center. It is also one of four bases in the Air Force to house both a Reserve unit -- the 932nd Airlift Wing -- and an Air National Guard unit -- the 126th Air Refueling Wing.