Troubled hedge fund Platinum Partners is the focus of another investigation.

Shareholders of Implant Sciences Corp., one of Platinum's investments, is calling for the firm to open its books about its dealings with the company, which filed for bankruptcy last month.

Shareholders of Implant, a Massachusetts company that makes and sells high-tech detector systems and devices that trace amounts of explosives and drugs, said in a court filing Tuesday that the company's primary source of debt was a series of bonds issued to a family of funds managed by Platinum. Court papers show the bonds were allowed to be converted into equity interests.

Implant is said to be a major position in Platinum funds, The Wall Street Journal has reported. Shareholders are requesting documents from Platinum and its affiliated funds for a deeper look into Implant's financial position, management and debt before the bankruptcy filing.

"First, these chapter 11 cases involve facts giving rise to a strong suspicion of wrongdoing that caused [Implant Sciences], and, in turn, their shareholders substantial harm," an attorney for the shareholders said in court papers.

A spokesman for Implant and a lawyer representing Platinum didn't immediately comment on the matter.

The shareholders are set to ask Judge Brendan Shannon to force the company, Platinum and its funds to hand over their books at a Nov. 29 hearing in U.S. Bankruptcy Court in Wilmington, Del.

Implant's bankruptcy-loan agreement requires the shareholders to wrap any investigation of Platinum and its affiliates by Dec. 23.

The affiliates, DMRJ Group LLC and Monstant Partners LLC, are both funds managed by Platinum. Before the bankruptcy filing, DMRJ and Monstant were part of the group that provided Implant Services with about $68 million in debt, court papers show.

Platinum's flagship fund sought chapter 15 protection on Oct. 18, days after Implant Sciences' chapter 11 filing. The hedge fund said in court papers that it has its legal operations in the Cayman Islands and has already appointed liquidators to wind down the fund.

The firm's liquidators have been in discussions with the U.S. Securities and Exchange Commission and the U.S. Justice Department regarding the potential sale of Implant's notes to "Platinum 'insiders,'" court papers said.

Implant Sciences, based in Wilmington, Mass., designs, manufactures and sells systems and sensors that detect trace amounts of explosives and drugs, according to court papers. Its customers include the U.S. Transportation Security Administration, the Canadian Air Transport Security Authority and European airports.

Write to Lillian Rizzo at Lillian.Rizzo@wsj.com

(END) Dow Jones Newswires

November 16, 2016 16:15 ET (21:15 GMT)