DETROIT ( TheStreet) -- In the first indication of February auto sales, General Motors reported an 11.5% increase, as sales of its four retained brands rose 32%.

The strong sales picture was tempered somewhat because retail sales for GM's four retained brands rose just 7% over a weak February one year ago. That means the bulk of the sales increase was due to fleet sales to businesses and rental car companies, typically at lower margins. Nevertheless, those sales signal a strengthening economy.

While sales rose at the retained brands -- Chevrolet, Buck, GMC and Cadillac -- sales fell by 64% to 98% at Hummer, Pontiac, Saab and Saturn, which are being discontinued.

The automaker attributed the increases to continued strong growth in sales of new crossovers and passenger cars. "Although we've been operating as a new company with four brands for just seven months, our February results demonstrate that our long-term plan is already paying dividends," said Susan Docherty, vice present for sales, service and marketing, in a prepared statement.

Among the highlights, February retail sales of GM's newest crossovers -- Chevrolet Equinox, GMC Terrain and Cadillac SRX -- were 198% higher than sales of the vehicles they replaced. Overall, Chevrolet sales rose 32%, with retail sales up 1%. Buick sales rose 47%, with retail sales up 18% and Buick LaCrosse retail sales up 100%.

At month's end, U.S. dealer inventory stood at 420,000, which is 30,000 higher than a month earlier and 361,000 lower than a year earlier -- a sign that a major structural flaw in auto industry methodology has been repaired.

Meanwhile, Ford ( F) said its Canadian sales rose 51% over the same month a year earlier, marking nine consecutive months of retail sales gains. Ford is expected to report U.S. vehicle sales around midday.

-- Written by Ted Reed in Charlotte, N.C. .