RALEIGH, WAKE COUNTY -

A federal grand jury is convening as part of a widening criminal investigation triggered by the massive Duke Energy coal ash spill that coated 70 miles of the Dan River with toxic sludge.

The grand jury is set to meet Tuesday at the federal courthouse in Raleigh. Prosecutors have issued at least 23 subpoenas to Duke executives and state officials.

U.S. Attorney Thomas Walker declined to comment, citing the secrecy of grand jury proceedings.

The subpoenas seek records from Duke, the North Carolina Utilities Commission and the state environmental agency.  They include reams of documents, including emails, memos and reports related to the Feb. 2 spill into the Dan River and the state's oversight of the company's nearly three dozen other coal ash dumps spread out at 14 power plants.