Officials have not said if anyone was hurt after American Heritage was partially submerged with 129 passengers on board.

A tanker has struck a river cruise boat carrying 129 passengers on the Mississippi River in New Orleans, partially submerging the vessel and prompting a major rescue operation.

The Atlantic Asphalt tanker hit the American Heritage paddleboat on Friday at about 12:30pm local time (18:30 GMT), the Port of New Orleans said. The cruise boat had docked about two hours earlier to begin letting passengers off. The authorities have not released any information on injuries or deaths.

“Multiple individuals have been rescued, and search-and-rescue operations remain ongoing,” a city spokesperson said.

Video from the scene showed the much larger tanker hitting the paddlewheel cruise boat as metal and glass crashed and crunched, according to The Associated Press news agency.

More than a dozen people in life jackets were dragged from the river, where the water temperature was 19 degrees Celsius (66 degrees Fahrenheit), onto nearby ships, while others stood near the railing as the boat listed further into the water.

“Surreal, that’s what that was,” one witness, Jamie Holford, told local television. “Fifteen minutes from impact to where it rolled over.”

Port police, the fire department, the coastguard and emergency medical staff are on the scene, and a triage area was set up inside the port’s administration building. The river was closed to vessel traffic.

American Cruise Lines, which operates the boat, said guests and crew had been evacuated and that it was “deeply concerned for everyone involved”.

The five-deck American Heritage, built in 2015, holds up to 150 passengers and was finishing an eight-day cruise to destinations in Louisiana and Mississippi.

The 160-metre (520-foot) tanker was flying the flag of the Marshall Islands and was bound for New Orleans, according to the MarineTraffic tracker. It specialises in carrying asphalt and bitumen, according to the maritime periodical Marine Insights.

The cause of the collision, as well as whether the ship was carrying cargo, remains unknown.