Firefighters battled large flames and heavy smoke Thursday morning, local officials said.
About 100 firefighters responded after the explosion and fire was reported about 7:30 a.m., said Western Lakes Fire District Assistant Chief Matt Haerter. Help came from as far away as Washington, Kenosha and Milwaukee counties.
Firefighters were expected to be on scene another eight hours, officials said. About 30 tanker trucks were bringing water to the scene because of a lack of fire hydrants in the area.
Kettle Moraine Fire District said crews were on the scene battling a blaze about 9 a.m. at W357 S8715 Chapman Lane in Eagle, Wisconsin, about 20 miles southwest of Waukesha.
There was a possible explosion before the fire began at Summerset Marine Construction, fire officials said.
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Two of the injured, including a firefighter, were taken to a hospital for treatment, including one who was seriously injured. Two other people and two firefighters were treated at the scene, Haerter said.
Twenty-four people were in the building when the fire broke out and all, including the injured, were outside by the time firefighters arrived, Haerter said.
With diesel and liquid petroleum inside the burning building, multiple explosions continued for about 30 minutes after firefighters arrived, officials said. Because the metal building on fire was in danger of collapsing, firefighters attacked the flames from the exterior.
Heavy smoke and large flames could be seen on the site.
Although the plant is in an industrial area, it isn't far from Eagle Elementary School, where students were evacuated and sent to the middle-high school in Palmyra.
Palmyra-Eagle Area School District Superintendent Todd Gray said the principal told him there was some shaking at the elementary school when the explosion occurred.
Officials advised those living within a mile of the factory to keep their windows closed due to smoke.
The company makes piers and docks, with a 24,000-square-foot (2,230-square-meter) facility in Eagle that includes a showroom, office, factory and warehouse, according to its website.
This is a developing story; check back with ABC7 Chicago for updates.
The Associated Press contributed to this post.