More than 1.3 million homes and businesses in New York and 1.4 million in New Jersey were still without power on Friday, four days after Hurricane Sandy slammed into the U.S. East Coast, power operating in those states said.

Most utility companies in the two states said it could take a week or longer to restore power to all customers in the wake of Sandy, the worst natural disaster to strike their customers, Reuters reported.

In New York, Gov. Andrew Cuomo sent a letter Thursday to the power companies’ CEOs, saying he would “take appropriate action against those utilities and their management if they do not meet their obligations to New Yorkers in this time of crisis.”

Consolidated Edison Inc., the biggest utility in the New York, said Friday about 565,000 homes and businesses in New York City and Westchester County were without power, down from more than 900,000 affected by the storm.

But the company warned that more than 100 buildings that have had their power restored were still without electricity due to flooding in basements or damage to local equipment.