OMAHA, Neb. (AP) — Warren Buffett's Berkshire Hathaway now controls nearly 20% of Occidental Petroleum's stock after picking up another $250 million worth of shares of the oil producer this week.

 Berkshire has been investing heavily in Occidental this year, including buying more than $1.2 billion of the Houston-based company's stock so far this month. 

After the latest purchases, Berkshire now holds nearly 180 million Occidental shares worth more than $10 billion.

 Buffett has been buying stocks aggressively this year as the market fell, including investing more than $51 billion in the first quarter alone.

By Associated PressOMAHA, Neb. (AP) — Warren Buffett's Berkshire Hathaway now controls nearly 20% of Occidental Petroleum's stock after picking up another $250 million worth of shares of the oil producer this week. Berkshire has been investing heavily in Occidental this year, including buying more than $1.2 billion of the Houston-based company's stock so far this month. After the latest purchases, Berkshire now holds nearly 180 million Occidental shares worth more than $10 billion. Buffett has been buying stocks aggressively this year as the market fell, including investing more than $51 billion in the first quarter alone.

Warren Buffett's firm buys more Occidental Petroleum shares