Over the past three days, Warren Buffet's company has invested another $350 million into the oil and gas company.

The conglomerate bought about 6 million shares at prices ranging from $57.67 to $616. The oil-and-gas company is valued at nearly $12 billion.

They saw the energy stock as a bargain again, so they resumed buying this week. It plummeted from a four-year high of $77 on August 29 to $61 at last check.

By March 16 of this year, the company's stake had grown to 136 million shares, or more than 14 percent of the total. In 35 trading days this year, it has built its entire position.

Vicki Hollub said that her company is strong in the US, that it is cutting its debts, and that it is buying back its stock.

She recently told Fortune that he likes the kind of company that returns value to shareholders.

However, the investor famously spurns hostile takeovers, and he hasn't talked to the company's bosses about a possible takeover.

About $2 billion has been made on paper so far, as a result of the $10 billion investment by the company. It received $5 billion in exchange for financing the oil group's takeover of Anadarko in 2019.