Cars are prepared for distribution at a Ford factory. Getty

U.S. auto industry sales weakened in May, with General Motors, Ford Motor and other manufacturers reporting lower U.S. vehicle sales for the month due to sluggish demand for sedans and fewer selling days.

Ford, which on Wednesday reported a 6 percent drop to 235,997 vehicles from a year earlier, estimated a sales decrease of about 8 percent for the U.S. industry in May.

GM, the largest U.S. automaker, said its sales fell 18 percent to 240,450 vehicles, a steeper decline than analysts had expected.

The sales reports spooked investors who have been on the lookout for weakness in the cyclical auto industry, which has been on an upswing since the Great Recession.

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Shares of Ford and GM were down about 3 percent in afternoon trading. The broader Standard & Poor’s 500 index and Dow Jones Industrial Average were down less than 0.2 percent.

Still, some analysts do not see the poor showing for May as the start of the anticipated weakness in auto sales, an early snapshot of consumer spending each month. Most analysts had expected a drop, in large part because of two fewer selling days and one fewer weekend last month.

“The outlook ... remains for another record year, and nothing in May’s results suggests otherwise,” said IHS Automotive analyst Stephanie Brinley.

Economic fundamentals remain strong and interest rates low, Brinley said.

Trucks and SUVs, which generally offer higher profit margins, remained the U.S. industry’s most popular vehicles, to the detriment of traditional sedans.

Ford U.S. sales chief Mark LaNeve said the skew toward the larger vehicles “really plays into Ford’s wheelhouse.”

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The same can be said for the two other major U.S. automakers, GM and Fiat Chrysler Automobiles, which also have strong lineups and sales of pickup trucks and SUVs.

Still, LMC Automotive analyst Jeff Schuster said that while midsize sedans made up a smaller share of the overall market, it was still sizable.

GM had slowed production at three plants that make sedans, which hurt May sales, the company said.

A year ago, the Cruze compact sedan was GM’s top-selling car, but its sales fell 30 percent in May. The Malibu midsize sedan, which gained 13 percent, replaced it as the company’s best-seller in that category.

Toyota Motor, No. 3 in the U.S. market behind GM and Ford, said its sales dropped 9.6 percent to 219,339 vehicles.

Cars’ share of Toyota’s sales fell to 49 percent from 53 percent in May 2015.

Honda Motor’s sales fell 4.8 percent, but counter to most automakers, the decline was steeper for its trucks and SUVs than for cars.

Ford’s car sales fell 25 percent. Sales were essentially flat for its SUVs and up 9 percent for its trucks. Sales for the best-selling vehicle in the U.S. market, the company’s F-Series pickup, rose 9 percent.

Among Ford sedan sales, the Fusion fell 21.5 percent, and the Focus dropped 27 percent. Sales rose 5.5 percent for the company’s top-selling SUV, the Escape.

FCA said its sales rose 1 percent to 204,452 vehicles on a 14 percent gain for its Jeep SUV brand. The company was the only major automaker in the U.S. market for which analysts had not expected a decline.

FCA’s Ram pickup truck sales fell 3 percent in May but were still up 8 percent for this year.

Nissan Motor said its sales fell 1 percent.

Forty economists polled by Thomson Reuters expect on average a seasonally adjusted selling rate of 17.3 million vehicles for May, not greatly changed from April but down from 17.8 million a year earlier.

In 2015, vehicle sales were a record 17.47 million vehicles, according to Autodata.