Questions are being raised about why Weet-Bix is no longer being supplied to The Warehouse.

The Commerce Commission's looking into Sanitarium's decision after it cited a ‘shortage’ for pulling the product from the red shed’s shelves.

Woolworths and Foodstuffs say they haven't had any conversations with Sanitarium about the move.

Grocery Commissioner Pierre van Heerden told Heather du Plessis-Allan it's unusual behaviour, and he would've expected adequate supply.

“I don’t see that overall suddenly by not supplying The Warehouse, there’s going to be lower demand. We’re still going to sell the same Weet-Bix within the country.”

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