U.S. businesses boosted their stockpiles by a slight amount in September while their sales increased by the most in three months.

The Commerce Department says business inventories edged up 0.1 percent in September, slower than the 0.2 percent gain seen in August. Sales were up a solid 0.7 percent, double the 0.3 percent rise in August. It was the best showing since a 1 percent gain in June.

The gain in sales was evidence that the economy is gaining strength after a sluggish period at the beginning of the year. Overall economic growth, as measured by the gross domestic product, increased at an annual rate of 2.9 percent in the July-September quarter, double the 1.4 percent GDP gain in the second quarter. Economists expect solid growth this quarter.