North Carolina regulators have cited five more Duke Energy power plants for lacking required storm water permits after a massive spill at one of the company’s coal ash dumps coated 70 miles of the Dan River in toxic sludge.

The state department of environment and natural resources announced Monday that Charlotte-based Duke had been issued formal notices of violation for not having the needed permits, which are required to legally discharge rainwater draining from its plants into public waterways.

Two other violations were issued Friday against the Dan River Steam Station in Eden, site of the 2 February spill. The company could face hundreds of thousands of dollars in fines for the violations.

State regulators indicated they had been aware since at least 2011 that some Duke facilities lacked the required storm water permits, yet took no enforcement action until after last month’s disaster.

Such a permit may have required testing and inspections that could have given early warning something was wrong with the pipe running under the huge coal ash dump at Eden before it collapsed. Tests performed on the water draining from a nearby pipe after the spill showed high concentrations of arsenic, an indicator that contaminated groundwater was leaking in from the dump above.

The violations were issued three days after the Associated Press filed a public records request for a copy of Duke’s storm water permit for the Dan River plant. The agency responded that no such permit existed.

Duke Energy did not immediately respond to a request for comment on Monday.

The five new violations are against Belews Creek Steam Station in Rockingham County, Cliffside Steam Station in Rutherford County, Lee Steam Electric Plant in Wayne County, Roxboro Steam Electric Power Plant in Person County and Sutton Steam Electric Plant in New Hanover County.

State regulators also expressed concern Friday about potentially contaminated water trickling from a stormwater pipe at the Cliffside plant. That pipe drains an emergency storm water basin built on top of an old coal ash dump, but is only supposed to drain water in severe storms.

State officials said the corrugated metal pipe is heavily corroded and taking in groundwater, which is draining out at a rate of more than 1,100 gallons a day into rocks a few feet from the Broad River.

Duke has 30 days to respond to the state on why the company feels the violations may be in error or why it should not be fined.