Volkswagen is facing multiple investigations in the United States, including, reports say, a criminal probe from the Department of Justice.
They follow an admission by the world’s biggest carmaker that it deceived US regulators in exhaust emissions tests.
A DoJ criminal investigation would be serious, as federal authorities can bring charges with severe penalties against a firm and individuals.
Late on Tuesday, New York state’s top lawyer announced an investigation.
New York Attorney General Eric Schneiderman said he would collaborate with other states to enforce consumer and environmental law.
“No company should be allowed to evade our environmental laws or promise consumers a fake bill of goods,” Mr Schneiderman said in a statement announcing the probe.
Meanwhile the Environmental Protection Agency and the California Air Resources Board are investigating the way VW cheated tests to measure the amount of pollutants coming from its diesel cars.
Volkswagen said 11 million vehicles worldwide were involved and it was setting aside €6.5bn (£4.7bn) to cover costs of the scandal.
According to news agencies Bloomberg and AFP, the DoJ is looking into the issue, which raises the possibility of the company and individual executives facing criminal charges.
However, the DoJ often extracts hefty payments from companies to settle criminal charges.
Volkswagen is due to hold a supervisory board meeting on Friday.
But reports say that chief executive Martin Winterkorn will appear before a select group of board members before then, possibly later on Wednesday.
On Tuesday, Mr Winterkorn issued a fresh apology for the test-rigging, saying he was “endlessly sorry” for the “manipulation”.
The boss of Volkswagen’s US business, Michael Horn, has also admitted the firm “totally screwed up”.
In the UK, the Department of Transport has added its voice to calls for an EU-wide investigation into the affair.