UPDATE 2-Duke shuts natgas plant due to Florence floods, coal ash leak feared

(Recasts, adds detail from state emergency management office on flooding)

Sept 21 (Reuters) - Duke Energy Corp said it shut down a North Carolina natural gas plant due to flooding as the deluge of water continued in the aftermath of Hurricane Florence, which has killed more than 40 people.

Duke also said it cannot rule out the possibility that coal ash from another plant is flowing into nearby waters.

Water breached the cooling lake dam at Duke's 625-megawatt natural gas L.V. Sutton plant, causing the company to shut the plant. Water is now exiting the cooling lake through breaches, one large and several smaller, the company said in a statement.

Site personnel are supplementing on-site supplies with large stones and other materials, and engineering experts are on their way to the site, Duke said.

Hurricane Florence brought several feet of rain to parts of North Carolina over a period of days, and the historic level of storm flooding is not expected to subside until next week.

Separately, company spokesman Paige Sheehan told the Associated Press they cannot rule out that ash might be escaping and flowing into the Cape Fear river from another plant. Reuters has not independently verified this information.

Duke reported two coal ash leaks from a retired plant in Wilmington, North Carolina, following storm Florence. One came from its shuttered Sutton Power Plant on Saturday and a second on Sunday, according to federal officials.

Officials had worried the water would overwhelm several pits where coal ash had been stored, potentially contaminating rivers.

Duke said there is no visible ash in the river. Coal ash collects at the bottom of basins, making it difficult to determine when ash escapes from a site.

Coal ash can contaminate water and harm fish and wildlife. Ash pits and other embankments have ruptured under heavy rain in the past, and Duke Energy had agreed to secure the sites in North Carolina's lowland areas - but that work is ongoing.

In 2015, Duke was fined more than $100 million after a 2014 spill that at the time was the third-worst coal ash spill in U.S. history.

The company's shares were down 0.9 percent at $79.87 in early afternoon trading. (Reporting by Ankur Banerjee in Bengaluru; Editing by Shounak Dasgupta amd Chris Reese)