Federal subpoenas obtained through a public records request show federal prosecutors are expanding their investigation of coal-ash containment in North Carolina.

The documents, obtained by Triangle news group WRAL, show the federal government is looking into Duke Energy's regulations of its 13 coal-ash storage ponds across the state, not just the pond related to the Dan River spill. The federal government is also asking for documentation of any payments to or from and communication between Department of Energy and Natural Resources employees and Duke Energy and subsidiary Progress Energy.

Read WRAL's full story, including the subpoenas, here.

• Duke Energy (flickr)
• Crews vacuuming coal ash from the Dan River