Performance Sports Group Ltd. fell as much as 66 percent to a record low after the athletic-equipment maker delayed filing its annual report because of an internal investigation, possibly resulting in a default on its credit lines, Bloomberg News reported yesterday. The shares tumbled to $1.18, the lowest since the stock started trading in 2011. Exeter, N.H.-based Performance Sports already had slid 64 percent this year through the end of last week. Performance Sports, a maker of baseball bats and hockey gear, said that its audit committee is conducting an investigation “in connection with the finalization of the company’s financial statements and the related certification process.” The committee has tapped independent financial advisers and retained Richards Kibbe & Orbe to provide independent counsel. The probe marks another blow for a company that already was reeling from the bankruptcy of Sports Authority Inc., one of its largest customers. In March, shortly after the retailer filed for chapter 11 protection, Performance Sports wrote down anticipated sales that it would have gotten from Sports Authority and slashed its financial forecasts.