Moody's Investors Service said Thursday it may downgrade the ratings on about $14 billion in debt held by FirstEnergy Corp.

Moody's said it does not expect FirstEnergy's senior unsecured debt rating, now Baa2, or two levels above junk status, to fall below investment grade.

Weaker than expected financial performance, the ongoing Davis-Besse nuclear plant outage, high debt levels and more prompted the debt review.

FirstEnergy remains committed to maintaining an investment grade rating, spokeswoman Kristen Baird said. The company will continue to aggressively pay down debt and improve its finances, she said.