LinkedIn, the social network for professionals, is believed to have received investment from a hedge fund that values the site at more than $2bn (£1.3bn).
Tiger Global Management paid $20m to buy a 1 per cent share from existing holders in the private company, according to Bloomberg.
This has almost doubled the site's value in just two years, after the private equity group Bain Capital took a 5 per cent stake in 2008 that valued the company closer to $1bn.
LinkedIn, which was set up by Silicon Valley entrepreneur Reid Hoffman in 2002, refused to comment yesterday.
This is not the first foray into investing in social companies for Tiger. In December, the alternative manager bought into Zynga, the social games company behind titles including Farmville. Mr Hoffman also holds a stake in the business, which, as well as LinkedIn is expected to float on the public markets.
LinkedIn, which turned profitable in 2007, hit four million members in the UK last month, after adding a million in less than eight months. It has more than 70 million users across more than 200 countries.
The group is run by Jeff Weiner, a former Yahoo! manager, and joined the group in June last year. Mr Hoffman remains chairman of the company he founded after selling PayPal to eBay for $1.5bn in 2002.
Mr Hoffman has invested in social network giant Facebook, which recently passed the milestone of 500 million members, news aggregator Digg and photo-sharing site Flickr. He also sits on the board of Gowalla, a location-based social network that competes with 4square.
Tiger is not particularly well known in the UK, although the New York group emerged as one of the hedge funds shorting the UK banks in 2008, after it took a short position in Bradford & Bingley.
It has recently looked at online operations in emerging markets. The fund invested $10m in Flipkart, an online book store focusing on the Indian market, in June, and last week it spent a further $10m for a 40 per cent stake in a Russian travel portal.Reuse content