The tender was opened on November 13 and the bidding deadline expired on December 11, the company said in a statement posted on the Zagreb Stock Exchange's website.
The sports hall, located in the Croatian capital, has been leased to municipal company Zagrebacki Holding for the next 27 years.
Ingra estimates its investment in the facility, completed in December 2008, at 100 million euro. The sports hall was built under a private-public partnership arrangement.
Ingra's shares, a component of the 24-share blue-chip Crobex index of the Zagreb bourse, were trading 4.54% lower at 42.50 kuna ($8.5/5.8 euro) by 1130 GMT on Monday.
(1 euro=7.2813 Croatian kuna)