Shares of energy giant First Gen Corp. plunged as much as 19 percent on Monday after its parent firm rejected a proposal from KKR to take the company private. The stock sank to P24.90 following a trading suspension, wiping out much of the recent rally sparked by buyout expectations.

Lopez family-backed parent firm First Philippine Holdings Corp. stated that KKR’s P35-per-share proposal did not represent the company's "true value." The rejected offer would have valued First Gen at roughly P126 billion and involved KKR acquiring additional shares to facilitate a delisting.

While the stock showed a partial recovery to P28, investors remain cautious. KKR, which is already a 19.9-percent shareholder, has yet to indicate whether it will return with a revised, higher bid for the public float.