China's Dalian Commodity Exchange on Tuesday asked members to act "rationally" in iron ore futures trade after prices for the steelmaking ingredient held above $100 per tonne.
"The iron ore market has been facing many uncertainties recently," the Dalian bourse said on its website, adding that it would strengthen investigations and strictly crack down on any irregularities.
Dalian's most traded iron ore futures contract, for September delivery, has jumped more than 8% since May 26 on concerns of tight supply from Brazil.
It closed at 757 yuan ($106.62) per tonne on Tuesday.
($1 = 7.0999 Chinese yuan renminbi)
(Reporting by Min Zhang and Tom Daly; editing by Jason Neely)