Focus Media Holding said the Securities and Exchange Commission is probing potential “violations” of securities law, with special attention to purchases and resales of companies including Allyes Online Media Holding.

The Shanghai-based advertising company is cooperating with the SEC, it said in a regulatory filing about its going-private transaction with Carlyle Group and other firms.

The Allyes deal, involving the swift resale of an acquisition of the Internet ad company back to the original owners, was one of a series queried in 2010 by the SEC.

Focus Media fell 80 cents, or 3.1 percent, to $24.99 in Nasdaq Stock Market trading yesterday.