Mr. LaHood later backed off that remark, and in a statement, Toyota stressed that problems with the sticking gas pedals were rare and assured owners not experiencing problems that Toyota felt “confident that your vehicle is safe to drive.”

That confidence was far from universal. Early on Wednesday, the Japanese government announced that it had ordered Toyota to investigate whether the brakes on new Priuses were working correctly after a recent spate of complaints. Those concerns were given a wider audience when Steve Wozniak, the co-founder of Apple, raised another concern about the Prius. He said that his 2010 model had “an accelerator that goes wild,” and suggested that software might be to blame.

Image Dave Otten, driving, with his fellow Prius carpoolers Elizabeth DiGirolamo, Ray Engeszer and Will Grant. Credit... Noah Berger for The New York Times

“It’s very scary,” Mr. Wozniak told CNET.com, “but luckily for me, I can hit the brakes.”

Other Toyota fans said they were spooked, too.

Tim Ahern, a spokesman for the environmental group the Trust for the Public Land, said he had bought a Prius for his commute from Sacramento  about 80 miles east of here  for the same reason cited by many buyers: Mother Earth.

“I was driving,” Mr. Ahern said. “But I was also doing something good for the environment.”

But on Wednesday, he said he was stunned that the Prius might have problems and had called his Toyota dealer for more information. Unfortunately, he said, there was little information to be had.

“So,” he said, “looks like I’m riding the train for a while.”

Some Prius lovers seemed prepared to fix whatever problem there might be and move on. Annie Sartor, the global finance director for the Rainforest Action Network, an environmental group, said she was unconcerned by the remarks by Mr. LaHood.