The fire broke out in the basement of the building in the area of some industrial dryers, Verdicchio said. It then spread through the ventilation system to the roof.
There were workers in the building at the time, but all of them escaped unharmed.
Fire Marshal James Totora said there is nearly 4 feet of contaminated water in the building that needs to be pumped out. The state Department of Energy and Environmental Protection also was on the scene Thursday to access the environmental impact on the nearby Housatonic River.
Latex International moved to the 208,000-square-foot building after a major fire destroyed its Ansonia factory in 2001. The company’s predecessor, Sponge Rubber Products Co., had a factory destroyed by arson in 1975.
Parent company Latex Foam International Holdings filed for bankruptcy protection this month.
The company produces latex mattress and pillows. It has more than 200 employees, including 170 at the Shelton plant.
Company officials released a statement saying they regret that several firefighters were injured and they plan to get operations back up and running as soon as possible.
“At this stage the company is working on ways of minimizing any disruption of service to its customers,” said David Fisher, president and chief executive officer of Latex International.