Investigators probing bankrupt retail giant Kmart Corp have impaneled a federal grand jury and issued more than 20 subpoenas for witnesses, it was reported on Sunday.

Quoting federal sources, the Detroit News said officials were focusing on alleged improprities by top executives, including former CEO Charles Conaway and former president Mark Schwartz.

The paper said matters being looked at include whether they misled board members about the company’s finances in the run up to its $2.4 billion bankruptcy filing in Janaury.

It added both Conaway and Schwartz are believed to have been interviewed by the FBI and that Kmart could sue the executives to recover some of the money they received before the Chapter 11 filing.

Other media reports said calls to the US Attorney's office Kmart were not immediately returned yesterday.