The road to recovery for Ohio's coal industry took an unexpected turn last year.

After four straight years of increased production, Ohio mining companies dug up nearly 10 percent less coal in 2006 than they did in 2005.

Mines produced an estimated 22.7 million tons of coal in 2006, compared with 25.2 million tons in 2005, according to the Ohio Department of Natural Resources' annual report on the state's mining industry.

State and industry officials say they can't explain what caused the drop, and they predict that mining will increase.

"It was really kind of surprising to me," said Lanny Erdos, Natural Resources' mine permitting manager. "I fully expect over the next two to five years for production to go up."

Erdos said new scrubbers and pollution filters that will be installed at Ohio coal-burning power plants and a push to build at least two new plants in Ohio has encouraged businesses to propose opening new mines in the state.

An underground mine that Gatling Ohio proposes for Meigs County in southern Ohio could produce as much as 2 million tons of coal annually, Erdos said. That mine would be near a 1,000-megawatt power plant that Columbus-based American Municipal Power wants to build near the Ohio River town of Letart Falls.

Another company, Ohio American Energy, wants to strip mine about 800 acres in Jefferson County in eastern Ohio, Erdos said.

Ohio's sulfur-rich coal has long been linked to pollution, including acid rain. Tougher federal air-pollution limits prompted power companies and businesses to burn lower-sulfur coal from other states as a cheaper alternative to scrubbers. That pushed Ohio's coal production down from a 1970 record of 55 million tons.

A Dispatch investigation published in December found that as coal production increased, the state lacked the money and manpower to oversee mines and to clean up more than 36,000 acres of abandoned mine lands.

Mike Carey, president of the Ohio Coal Association, an industry group, said the dip in production is not significant. He said lengthy waits mining companies face to get federal permits needed to open new mine sites might have been a factor.

"It's hard to judge from year to year," Carey said. "We'll have a better picture after 2007."

shunt@dispatch.com