Omaha: Warren Buffett's company is apparently bullish on the US auto industry. Berkshire Hathaway took a new 10-million share stake in General Motors in the first quarter. The investment comes as the Detroit automaker continues to rebound from bankruptcy three years ago. Fuelled by US vehicle sales, it posted first-quarter net income of $1 billion.

Buffett drives a GM-made Cadillac DTS sedan, so the investment could be a further sign of his preference among US automakers. Berkshire is not invested in Ford Motor or Chrysler, which is majority owned by Fiat. But the purchase of the GM stake, worth about $214 million as of Tuesday, could also have been made by one of Berkshire's other investment managers. Berkshire's only other known auto investment is its roughly 10 per cent stake in Chinese electric car maker BYD.

Omaha-based Berkshire also revealed in a regulatory filing on Tuesday that it boosted its stake in Wal-Mart by almost 8 million shares to 46.7 million shares. The first-quarter move to expand Berkshire's stake in Wal-Mart came before The New York Times published a report detailing allegations that Wal-Mart executives used bribes to speed the retailer's expansion in Mexico.