Uralkali has offered to pay 5 billion rubles ($140 million) toward the cost of a rail bypass around a damaged mine, bringing its total costs related to the accident to 7.8 billion rubles.

The potash miner's London-traded stock soared more than 28 percent on the news, which eased investor fears that the company could face crippling damages after the government unexpectedly reopened an investigation into the 2006 flood of the company's Mine 1.

Uralkali said Tuesday that the cost of building the 53-kilometer rail bypass was estimated at 12.33 billion rubles.

The federal budget would contribute 2.79 billion rubles to the total cost, Russian Railways 3.54 billion rubles and rival potash miner Silvinit 1 billion rubles, the company said in a statement.

Silvinit's supplies came under threat after the flood at the Uralkali mine in the Ural Mountains, which opened up a sinkhole that encroached on a nearby rail line used by both producers.

At the meeting, Uralkali president Anatoly Lebedev reiterated a separate pledge to pay 2.77 billion rubles, an amount that represents the revised costs related to the accident incurred by the federal and regional governments and Russian Railways.

Uralkali also said it would pay about 36 million rubles to the municipal budget of Berezniki, where the mine is located.