IndyCar chief operating officer Marc Koretzky resigned Thursday, effective immediately.

IndyCar did not give a reason for Koretzky's resignation, and said his responsibilities will be split among current staff members for the time being.

Koretzky joined IndyCar in May 2011 as director of business development. He led the management of commercial activities and non-racing events around last season's finale in Las Vegas.

He was promoted to COO in December, replacing Terry Angstadt. His role was to oversee the day-to-day organizational operations of IndyCar. Koretzky was also responsible for fostering communication and synergies across the company's commercial and operations units.