Social networking website Twitter has confirmed that it has closed a "significant round of funding".
Co-founder Evan Williams said in a blog post that the site had secured money from five investment companies.
However, he did not confirm earlier reports that suggested the firm had managed to secure $US100 million, which would value the firm at $US1 billion.
The site has more than 45 million users worldwide.
Twitter previously raised $US35 million in February in a deal that valued the business then at $US255 million.
Industry watchers have pointed out that the company still has no way of making money. However, earlier this month the site revised its terms and conditions to allow advertising on its service.
The new funding has come from new investors Insight Venture Partners and T Rowe Price, as well as existing backers Institutional Venture Partners, Spark Capital and Benchmark Capital.