SAN FRANCISCO (

TheStreet

) --

Twitter

is close to securing $100 million in funding from new investors

T. Rowe Price

(TROW) - Get Report

and private-equity firm Insight Venture Partners, a report says.

Existing Twitter investors, including Spark Capital and Institutional Venture Partners, are also expected to participate in the latest funding round for the microblogging site, the

Wall Street Journal

reports, citing people familiar with the plan.

The investors are valuing Twitter at about $1 billion, or more than triple the valuation Twitter received during the last time it raised capital in February, the

Journal

reports.

Twitter has seen the number of visitors to its service soar to 54.7 million unique visitors worldwide in August, up from 4.3 million in August 2008, according to data from comScore.

Twitter's growth has caught the eye of companies such as

Google

(GOOG) - Get Report

and

Microsoft

(MSFT) - Get Report

, which have pitched Twitter on potential arrangements to help it sell advertising, the

Journal

says.

Speculation also has grown that Twitter will one day be acquired by a larger Internet player. Twitter has maintained its desire to remain independent.

Twitter didn't respond to requests for comment from the

Journal

.

-- Reported by Joseph Woelfel in New York

.

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