Officials in the U.S. states of New York, New Jersey and Pennsylvania on Thursday said at least 40 people had died as a result of flash flooding caused by torrential rainfall driven by remnants of Hurricane Ida.

Officials in New York City said as many as 15 people had died while trapped in basement apartments by floodwaters or caught in their cars.

The storm system that came ashore Sunday in Louisiana as a Category 4 hurricane dumped so much rain in the Northeast U.S. that on Wednesday the National Weather Service issued its first flash flood emergency for New York City and the neighboring city of Newark, New Jersey. At least 23 people died in New Jersey, and at least five perished in Pennsylvania.

Many streets were quickly turned into rivers, submerging cars and even commuter buses. Most of the city's subway system was shut down by the flooding.

Danny Hong shows where floodwater reached up to him as he shows the damage in his basement apartment in the Flushing neighborhood of the Queens borough of New York, Sept. 2, 2021.

New York Governor Kathy Hochul spoke with reporters after touring the city and noted the record-setting eight centimeters of rain that fell in one hour in New York's Central Park, breaking a record set just one week earlier.

"We did not know that between 8:50 and 9:50 p.m. last night, that the heavens would literally open up and bring Niagara Falls' level of water to the streets of New York," said Hochul, who became governor last week after former Governor Andrew Cuomo resigned.

This kind of cataclysmic event, she added, is no longer unforeseeable, and the city and state need to be prepared.

A motorist drives a car through a flooded expressway in Brooklyn, New York, early on Sept. 2, 2021, as flash flooding and record-breaking rainfall brought by the remnants of Hurricane Ida swept through the area.

Biden pledges federal aid

Speaking at the White House, U.S. President Joe Biden pledged emergency assistance to governors of New Jersey and New York as well as other states in the region and sent his condolences to the families of those who lost their lives.

He also said he would be traveling to Louisiana on Friday to meet with Governor John Bel Edwards to discuss the recovery efforts from Ida there. The president said the nation's Federal Emergency Management Agency and other agencies would be working around the clock until the needs of the region were fully met.

A police officer stands guard as a man surveys the damage to a home where people died after their basement apartment flooded, in the Jamaica neighborhood of the Queens borough of New York City, Sept. 2, 2021.

Biden noted the region hit by Ida is a key center of the nation's oil production and refining infrastructure. He said the government was moving quickly to make sure gasoline continued to flow throughout the country.

"We're all in this together," Biden said Thursday at the White House. "The nation is here to help."

The president also called extreme storms and wildfires burning in the West a reminder that climate change is here, and he urged Congress to pass his infrastructure bill, which contains measures to address it.

Some information for this report came from The Associated Press and Reuters.