Something at HBK Investments has attracted the attention of the Securities and Exchange Commission. According to TheStreet.com, the Dallas-based hedge fund is the focus of an investigation of alleged improper trading of private investments in public equity, or PIPEs, in connection with Plug Power. At issue is whether HBK engaged in insider trading by short selling the companys stock in 2003 right before an initial public offering. HBK, which according to PrivateRaise.com is the ninth-largest PIPEs HF investor with more than $56 million in the first quarter of 2006, is not the only hedge fund been involved in PIPEs matters. The SEC has slapped two other hedge funds with PIPEs-related fines of $22 million, and an additional three have received SEC subpoenas. In addition, Mangan & McColl Partners, the Charlotte, N.C., hedge fund that announced it was closing its doors at the end of the month, has been investigated by the NASD for potential PIPEs violations relating to naked short sales in 2001 of Compudyne.