New York’s Attorney General has launched an investigation into hundreds of complaints of prices being increased in the aftermath of Hurricane Sandy.
Eric Schneiderman said the largest number of complaints concerned increased fuel prices, but other emergency supplies were also affected.
“Price gouging” of essential consumer goods is forbidden under New York law.
More than one million people in New Jersey and New York are still without power a week after the storm hit.
Although fuel supplies are reaching petrol stations across the region, around one-quarter are still closed in metropolitan New York.
At the weekend, long queues of cars and people carrying red canisters built up at petrol stations.
As a result of the storm, 8.5 million homes and businesses were left without power, prompting a surge in demand for generators and hotel rooms. Tens of thousands of people have been displaced.
Eric Schneiderman said that consumers had contacted him to report “possible gouging for emergency supplies like generators, hotels raising rates due to ‘high demand’, as well as increased prices for food and water”.
In a statement, the attorney general said that under New York state law, retailers were not allowed to charge “unconscionably excessive prices” for goods required for personal, family or household purposes when there was an abnormal disruption of the market.
He pledged to do “everything we can to stop to stop unscrupulous individuals from taking advantage of New Yorkers trying to rebuild their lives”.
Transport authorities opened more subway lines on Monday, as more commuters returned to work and one million students returned to school for the first time since the storm.
But platforms were teeming with travelers, trains were overcrowded and limited bus services struggled to meet the demand for services into New York City.
Hundreds of people joined queues early on Monday for the Jersey City ferry service to New York.
As overnight temperatures fell close to freezing, forecasters warned of a new storm approaching the US east coast.
According to the National Weather Service, the coastal storm could reach South and North Carolina late on Tuesday before spreading northwards, strengthening as it moves up towards New Jersey with gusts of up to 50 mph (80 km/h) by Thursday.
“Prepare for more outages,” Weather Service meteorologist Joe Pollina told Associated Press.