An international mining company says production in north-west Queensland is not being affected by one of its ships being out of operation.

The ship carries MMG's zinc concentrate from the Karumba Port, north-east of Mount Isa, to an export vessel but it lost its rudder last week.

MMG spokesman Mark Adams says its workers noticed last week the 1.6 million tonne rudder had gone from the ship, forcing them to suspend operations.

Mr Adams says they have ordered a new rudder from Germany while they search for the missing one.

"We bought the ship back into port obviously for a risk assessment, but for safety reasons we're suspending operations," he said.

"At the same time we're looking for the rudder, we're doing both a side scan sonar survey and a magnetic survey - both which are under way at the moment."

He says in the meantime the zinc concentrate can be stored in a shed at Karumba.

"Karumba will continue to process to the 24th of this month," he said.

"We've got plenty of space in the shed and then we shut down for a week ... if we don't find the old rudder the new rudder will be available to us."