Manufacturers in 11 of 21 industries reported lower sales, representing more than 60 percent of total manufacturing.
After four consecutive months of increases, sales of transportation equipment declined 6.4 percent to $8.6 billion, the report said.
"A 22.1 percent drop in aerospace product and parts led the decline, followed by a 3.2 percent decrease in motor vehicle assembly," StatsCan said.
Half of the 10 provinces posted sales declines. Ontario led with a 1.9 percent drop to $22.3 billion, based on fewer sales in motor vehicle assembly, machinery and primary metals.
Quebec was second in the loss of volume of manufacturing sales, down 2.6 percent to $11.3 billion, the report said.
The month's overall decrease was the third in five months, the agency said.
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