Not enough coal is being produced to fill the number of ships waiting to be loaded off north Queensland.
The ABC reports about 41 ships are anchored off the Mackay coast.
But Integrated Logistics Company says there is enough coal to fill only 12 ships.
The ship queue for the Dalrymple Bay terminal peaked at 69 ships earlier this year.
Company spokesman Mario Checuti says the drop in production does not appear to be an attempt by mining companies to artificially inflate prices.
