Investing.com-- Google owner Alphabet Inc shares are headed for strong gains on Monday, 24-hour trading data showed, after Warren Buffett's Berkshire Hathaway disclosed a $4.3 billion stake in the firm.

Alphabet Inc (NASDAQ:GOOGL) shares rose 6.1% to $293.40 in afterhours trade, 24-hour trading data from Robinhood showed on Sunday evening. The stock had risen as far as 7%.

Gains in the stock come after Berkshire Hathaway (NYSE:BRKa) late last week disclosed it had taken a $4.3 billion stake in the Google parent, making it its tenth-largest U.S. stock holding.

The hedge fund further trimmed its stake in Apple Inc (NASDAQ:AAPL) and Bank of America Corp (NYSE:BAC). Apple still remained the hedge fund's largest stock, even as the firm steadily trimmed its holdings this year and built up its cash balance.

The rationale behind the Alphabet acquisition was not immediately clear. Buffett had in 2019 lauded Alphabet's advertising business, and had also lamented not investing in the firm earlier.

Berkshire's investment in Alphabet comes despite growing concerns over stretched tech valuations, especially due to hype over artificial intelligence. This notion had weighed heavily on tech shares through late-October and early-November.

Alphabet, in late-October, clocked stronger-than-expected earnings, but also hiked its capital expenditure outlook on expectations of more AI spending.

The company over the weekend said it will invest $40 billion to build new data centers in Texas.