Continuing its growth spurt, mobile billing and messaging company MBlox Inc. has closed a $22 million fifth round of funding to expand its product line and eye other companies for possible mergers and acquisitions.

The new round was led by an undisclosed institutional investor, said MBlox Chief Marketing Officer Steve Livingston. Joining in the round were past investors Norwest Venture Partners, Novus Ventures, Scale Venture Partners, Avanti Capital, Trident Capital, Entrepreneur's Fund and Duff Ackerman & Goodrich.

MBlox has raised a total of $65.6 million in venture funding since 2001, VentureWire records show.

The newest round "gets [MBlox] closer to the public markets," Livingston said. He added that the company was "exploring the option" of going public, but was also looking at merger possibilities or snapping up other companies.

"M&A, in our business, means expanding geographically," Livingston said.

MBlox merged with SMS provider MobileSys in 2003 in a deal with undisclosed terms, records show.

The company - with offices in Sunnyvale, Calif.; Dusseldorf, Germany; Madrid; Sydney, Australia; Stockholm; and Paris - has between 250 and 300 employees, Livingston said.

MBlox facilitates transactions between mobile customers and third-party content providers, for instance companies selling ringtones and games. This frees up wireless carriers to concentrate on more pressing matters, the company has said.

MBlox's revenue comes from sharing the proceeds from sales between content providers and carriers. In 2006, the company counted some 1.4 billion completed transactions, with $500 million changing hands. Revenue at MBlox has gone up about 40% per year, Livingston said, declining to provide specific figures. The company has done business with some 500 mobile carriers, he said.

"We haven't closed the books on 2007 yet, but our growth rate is still on the same trajectory," he said. While he would not discuss the company's valuation, Livingston said this was "a significantly up round."

The new round brings no new members to the board at MBlox, Livingston said.