Holding Varna has offered 9.97 levs ($7.14/5.09 euro) per share, the Financial Supervision Commission (FSC) said in a statement.
Ownership in St. St. Constantine and Helena is divided among a number of small shareholders, the biggest of which is local company Andenzit with a 28.17% stake, according to the latest data available. Holding Varna is the third biggest shareholder with a 5.0% stake.
Shares in St. St. Constantine and Helena closed down 6.6% at 12.99 levs on Tuesday. The commission's statement was released after the end of trading.
Earlier this year Holding Varna raised some 69 million levs for investments in a capital hike.
Holding Varna stock lost 0.35% to 13.95 levs on Tuesday.
(1 euro = 1.95583 Bulgarian levs)