A further 17,000 tonnes of concentrate was sitting idle at the mine site.

Ivernia shut the mine down and declared force majeure on shipments after exports from Esperance were stopped on March 12 following the death of some 4,000 birds, possibly caused by lead poisoning, leaving the 9,0000 tonnes of lead stranded.

Western Australia's Department of Environment and Conservation. (DEC) was investigating the deaths.

Also, a Western Australia state inquiry is looking at why Ivernia transported and exported lead carbonate through the port in a powdered form rather than in pellets.

Mine operator Magellan Metals this week told the inquiry it recognised lead carbonate from its mine transported through the port had escaped.

When the mineral was transported the hundreds of kilometres from the mine to Esperance, the agglomerates dried up and reverted to powder, it said.

Ivernia has proposed packing the 9,000 tonnes of lead stuck in Esperance in individual one-tonne sealed bags before being shipping it to buyers in China, where the material is smelted into lead metal.

The proposal is to be presented to the DEC for approval following the public consultation, the spokesman said.

Longer term Ivernia hopes to win approval to resume shipments from the mine employing air-tight containers, the spokesman said.

The spokesman reiterated earlier comments by the company that any alternative shipping arrangements could take three to four months to initiate.

A DEC spokeswoman said monitoring by the department was continuing on shipments of nickel concentrate from the port after expanding the probe last month.

The Magellan mine was set to supply about 3 percent of the world's mined lead at full production.

Businesses declare force majeure when they can't meet supply contracts because of forces beyond their control.