Icahn Enterprises faces setbacks amid federal investigation and short seller attacks.

Hindenburg Research announced a new short position in Icahn Enterprises (IEP) bonds, causing the stock to drop roughly 5%. This comes after Hindenburg revealed a short position in IEP common shares on May 2. Icahn Enterprises also disclosed that a federal probe into its business began the day after Hindenburg’s first short report. Billionaire activist-investor Carl Icahn responded to Hindenburg via a statement, but Hindenburg clapped back on Thursday, specifically targeting Icahn’s personal loans taken out using IEP shares as collateral.