Apple Inc's stock hit an all-time high on Friday after Warren Buffett's Berkshire Hathaway Inc disclosed it had bought 75 million more shares of the iPhone maker in the first three months of the year.
Buffett's increased stake, confirmed by a representative of the billionaire investor, pushed Apple's shares up as much as 3.8 percent to $183.65.
It was the stock's second significant gain this week after the Cupertino, California-based firm surprised Wall Street on Tuesday with resilient iPhone sales and quarterly results that topped expectations.
"If you look at Apple, I think it earns almost twice as much as the second most profitable company in the United States," Buffett told CNBC, which first reported the news on Thursday.
Buffett's Apple commitment over the past two years has surprised many, given his historical aversion to companies associated with the technology sector.
Berkshire's initial investment in Apple was small, suggesting it was made by one of Buffett's investment deputies, but with the latest stake purchase, it has grown to a massive 240.3 million shares worth $42.5 billion.
In February, Berkshire had said its Apple stake grew by about 23 percent since the end of September to roughly 165.3 million shares.
The billionaire investor recently sold out of an unsuccessful investment in IBM Corp, at the same time he was buying Apple.
Buffett has praised Apple Chief Executive Officer Tim Cook and suggested he views Apple more as a consumer company, despite its Silicon Valley pedigree.
However, there may also be another reason for the investment: Berkshire's cash position.
Berkshire has gone more than two years since a major acquisition, and Buffett said in his annual letter that he wants one or more "huge" non-insurance acquisitions to help him reduce Berkshire's $116 billion in cash and equivalents.
Buying Apple accomplishes that, even though Buffett would rather buy whole companies than their stocks.
Berkshire typically discloses its largest common stock holdings and percentage stakes in its quarterly and annual reports. The report for the first quarter is scheduled for release on Saturday morning, just before Berkshire's annual shareholder meeting in its Omaha, Nebraska hometown.
Apple reported $61.1 billion in revenue for the March quarter, up from $52.9 billion last year, and promised $100 billion in additional stock buybacks.
Apple did not immediately respond to a request for comment on Friday.
Up to Thursday's close, Apple stock had risen more than 5 percent since Berkshire disclosed on Feb. 14 that it had raised its stake in the company.