INDIANAPOLIS (AP) - Environmentalist say that Indiana's largest electric utility needs to move faster to retire its aging network of coal-fired power plants and replace them with cleaner, more renewable power sources.

Duke Energy Indiana officials say they hope to retire all nine of the utility's coal-fired units by 2038 and construct two large natural-gas plants.

But the Indianapolis Business Journal reports that environmentalists contend Duke is stalling and that other Indiana utilities are moving faster to mothball the plants, which spew carbon dioxide and other pollutants into the atmosphere

Environmentalist say the climate is getting warmer and weather is becoming more severe.

Other state utilities such as Merrillville-based Northern Indiana Public Service Co. noted last fall it plans to retire four of its five remaining coal-fired power units within five years.