The top automakers in the U.S. market each disclosed lower sales in April compared to the same month last year.
Last month included one less selling day than April 2016, but analysts suggested that the numbers could indicate slowing demand after record vehicle sales last year.
Detroit's "Big Three" — General Motors, Ford and Fiat Chrysler — saw sales declines of 5.8 percent, 7.2 percent and 7 percent, respectively, compared to the same month in 2016.
Their largest overseas competitors didn't fare much better. Honda also fell by 7 percent, while Toyota sales dropped by more than 4 percent. Nissan sales slid by a more modest 1.5 percent.
Those six companies accounted for more than 75 percent of the U.S. auto market in March, according numbers from The Wall Street Journal.
The totals come amid projections showing that sales for the year could fall short of 2016's record. In addition, a recent report indicated that vehicle inventories were at their highest levels in more than a decade.
Although automakers told the Associated Press that sales and vehicle prices remains strong, indicators suggest that dealer incentives could be beginning to take their toll on prices — which could hurt automaker profits.