Aug. 28--From the outside, the power plant that towers above Chicago's Pilsen neighborhood looks like a sooty relic from the early part of the last century.

The Fisk plant has been burning coal to generate electricity on the Near West Side since 1903. But federal and state lawyers alleged Thursday that its internal parts -- the massive boiler, steam chest and turbine -- have been repeatedly upgraded without the modern pollution controls required under the Clean Air Act.

By steadily replacing worn out equipment, a lawsuit filed in U.S. District Court alleges, owner Midwest Generation kept Fisk and five other power plants operating well past the time when they otherwise would have been closed. The noxious smoke churning out of the plants makes them some of the biggest contributors to dirty air in the Chicago area, according to federal records.

The 75-page lawsuit marks a renewed effort by the Obama administration to crack down on emissions from coal-fired power plants, an undertaking that languished under former President George W. Bush. Coal plants are major sources of heat-trapping carbon dioxide, toxic mercury and other pollutants that create lung-damaging soot and smog.

Besides the Fisk plant, the suit cites the Crawford plant in Chicago's Little Village neighborhood, and plants in Joliet, Romeoville, Waukegan and Downstate Pekin.

Targeted repeatedly by neighborhood activists and environmental groups, the Midwest Generation plants have avoided anti-pollution regulations for years, in part because federal regulators assumed decades ago that the aging generators would have been scuttled by now. In 2001, a Harvard School of Public Health study estimated the Fisk and Crawford plants alone are responsible for 2,800 asthma attacks, 550 emergency room visits and 41 early deaths every year.

Four years later, Illinois Atty. Gen. Lisa Madigan documented thousands of pollution violations at the power plants. She joined the lawsuit filed Thursday by the U.S. Justice Department on behalf of the U.S. Environmental Protection Agency.

"I am very concerned about the negative health effects that these aging plants have on the people who live in the communities where the Midwest Gen facilities are located," Madigan said.

Company officials contend the problems outlined in the complaint are being addressed. Under a 2006 deal with the Illinois EPA, Midwest Generation agreed to clean up or close its coal plants by 2018. The federal lawsuit could force the company to upgrade or close its plants faster.