Mississippi Power Co. has named Ed Holland as president, replacing Ed Day.
The subsidiary of Atlanta-based Southern Co. said Monday that Day is retiring and will be replaced immediately.
Northern District Public Service Commissioner Brandon Presley says Holland told a PSC lawyer last week that Day directed or allowed Mississippi Power employees to withhold documents from regulators about a $366 million cost overrun.
That increase was announced weeks after commissioners voted in 2012 to reaffirm the company's license to build a lignite coal plant in Kemper County.
A spokeswoman didn't immediately respond to questions about Presley's account.
Overruns announced last month raised the cost of the plant, mine and pipelines to $4.3 billion. Shareholders will absorb that $540 million increase.
Presley says it's a good sign that Holland, Southern Co.'s general counsel, is taking over as CEO.