NEW YORK (REUTERS) - Hurricane Ida's death toll in the US Northeast rose on Sunday (Sept 5) to at least 50 people, with many holding out hope for the missing in the floodwaters and Pope Francis calling on those affected by the disaster to be strong.

Ida's record-breaking rainfall of 3.1 inches (7.9cm) per hour, recorded in New York City's Central Park on Sept 1, sent walls of water slamming through businesses, public transportation systems and 1,200 homes, causing more than US$50 million (S$67.05 million) in damages, Governor Kathy Hochul said.

New York had 17 confirmed deaths, four in Westchester County and the remainder in New York City, where nearly all the victims were trapped in illegal basement apartments that are among the last remaining affordable options for low-income residents in the area, a spokesperson for Governor Kathy Hochul said.

"The human toll was tremendous," said Hochul, recounting a trip to East Elmhurst in the city borough of Queens to assess the devastation.

"One woman wept in my arms, an 89-year-old woman. She had nothing left after living in that home for over 40 years," Hochul said.

New York's governor had previously secured an emergency disaster declaration from President Joe Biden and on Sunday signed paperwork to request related federal money to cover the costs of temporary housing as well as rebuilding homes, possibly in less flood-prone locations.

In New Jersey, there were 27 confirmed storm deaths and four people still missing, said a spokesperson for Governor Phil Murphy.

Among the missing were two college students last seen in Passaic, New Jersey, on Wednesday as Ida's historic deluge was reported to have swept them away in the floodwaters of the raging Passaic River.

Twelve boats searched the river on Sunday as part of round-the-clock operations, and rescue teams were anticipating specialized high-resolution sonar to aid their search on Tuesday and Wednesday, the Passaic fire department said.

A student mass was called on Sunday at Seton Hall University in South Orange for Nidhi Rana, a first-year commuter student from Passaic who was last seen with her friend Ayush Rana, a Montclair State University student, as the water rushed around his car.

"Join me in keeping Nidhi and Ayush in your prayers for their safe return," Seton Hall President Joseph Nyre said in a letter to students.

Neither the Passaic Police nor the Fire Department immediately responded to Reuters' requests for more information.

Other Northeast states where storm deaths were reported included Connecticut with at least one dead, Pennsylvania with at least four dead and Maryland with at least one dead.

Louisiana's governor on Saturday increased the number of storm deaths in his Gulf Coast state to 13 people killed after Ida made landfall there on Aug 29 as a Category 4 hurricane, downing trees, power lines and debris with wind gusts that reached 172 miles per hour (276 kph).

At least four of those people died in Louisiana of carbon monoxide poisoning from power generators, officials said.

Amid stifling heat and humidity, more than 591,000 homes and businesses in the state lacked electricity as of Sunday, according to PowerOutage.com. Some 1.2 million had originally lost power.

Ida also paralyzed US Gulf of Mexico oil production, and 88 per cent of crude oil output and 83 per cent of natural gas production remained suspended as of Sunday.

The Grand Classica, a cruise ship that will house 1,500 workers trying to restore power, departed from the Port of Palm Beach on Saturday and is due to arrive in New Orleans on Tuesday under a charter agreement with Entergy Corp., the Bahamas Paradise Cruise Line said.

A massive oil slick has emerged near the oil hub of Port Fourchon, Louisiana, with satellite images showing a miles-long brownish-black slick spreading in the coastal waters. A private dive team was attempting to locate the source.

Pope Francis offered his condolences to Ida victims at his Sunday blessing in St. Peter's Square.

"May the Lord welcome the souls of the dead and give strength to those who are suffering from this calamity," the Pope said.