Flint’s mayor, Karen Weaver, said that she was alarmed at hearing that the companies may have been at fault, and appreciative of the continuing investigations. “It’s disturbing to hear that companies hired to ensure the safety of the city’s water supply may not have done what they were paid to do,” she said, adding that the city is still under contract with LAN, an engineering company based in Houston, which she said had received nearly $3.5 million from the city for work before, during and after the switch to the Flint River.

Veolia, an international water management company that is a subsidiary of a France-based company, had a $40,000 contract, a city spokeswoman said, and also received about $15,000 for work a few years earlier.

Advocates for the environment said Veolia had been accused of violations elsewhere, including polluting waterways and overbilling customers, leading to lawsuits filed in courts across the country. Residents were skeptical of the quality of its work in Flint.

“I don’t have a Ph.D., but I know that if the water is brown, that means the pipes are getting torn up and something is causing the pipes to be torn up,” said Melissa Mays, a Flint resident who has protested the water conditions. “They should have figured out what it was.”

The two companies denied the attorney general’s characterization of events and defended their efforts in Flint, though neither company made executives available to be interviewed.