The auditor of billionaire Gautam Adani’s ports business is planning to resign, people familiar with the matter said, a move that may heighten concerns about accounting quality at the Indian conglomerate targeted by short seller Hindenburg Research.

Deloitte Haskins & Sells LLP has communicated to Adani Ports & Special Economic Zone Ltd. its resignation plans and a formal announcement is expected in coming days, one of the people said, asking not to be identified discussing a sensitive matter.