Twitter is close to securing as much as $100 million of new funding from up to seven investors in a deal that values the fast-growing microblogging site at about $1 billion, the Wall Street Journal reported on Thursday.

The funding group includes mutual fund giant T. Rowe Price and private equity firm Insight Venture Partners, both new investors to Twitter, the Journal said, citing people familiar with the deal. The story also said the group included Spark Capital and Institutional Venture Partners, which have previously put money into the company.

If it goes ahead, the $100 million investment -- twice as much as Twitter had been expected to get in its latest round of fundraising -- would underscore investors' interest in the two-year old company, which hosts short, stream-of-consciousness text messages on its website.

Institutional Ventures declined to comment.

The other investors and Twitter, which ThomsonReuters data show has secured $57.85 million of funding through various financing efforts, were not immediately available to comment.

Twitter, which Google chief Eric Schmidt once called the poor man's email, and other social networking sites have become cultural sensations. But many are hard-pressed to show they are viable businesses, or that they have what it takes to eventually go public or snag buyers.

Worldwide visitors to Twitter's site hit 44.5 million in June, up 15-fold from a year earlier, according to comScore data. But the San Francisco-based company has only just begun to focus on making money from its free service.

This week, founder Biz Stone said Twitter would not take advertising this year, despite widespread speculation that it would.

Investors are now applying a similar value to Twitter as they did to Facebook, the Journal said, citing a source familiar with the deal.

Twitter's past investors included Benchmark Capital and Union Square Ventures, Charles River Ventures and Bezos Expeditions, according to ThomsonReuters data.

A February round of funding, led by Institutional Venture Partners and Benchmark Capital, had valued the company at about $250 million. The pair jointly invested $35 million in Twitter during that round.

Twitter's tweets are 140-character text messages published to subscribers or followers. The service has become a phenomenon among news junkies, Hollywood watchers -- and many investors.

Both President Barack Obama and Senator John McCain used Twitter to communicate with voters in the 2008 presidential campaign.

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