A 9.6 per cent drop in sales in the petroleum and coal industry reflected temporary shutdowns at some refineries.
The agency says the drop was offset by gains in the aerospace product and parts industry.
In all, sales fell in 13 of 21 industries, representing approximately two-thirds of manufacturing.
Four provinces accounted for the drop in sales, with Ontario and Alberta posting the largest declines in dollar terms.
Meanwhile, inventories rose 2.1 per cent in May to $66 billion and StatsCan says total inventories were at their highest level since January 2009.
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