More than 4,200 people trapped aboard the crippled cruise ship Carnival Triumph, having endured days of overflowing toilets, were expected to return to land late last night when tugboats hauled the vessel into Mobile, Alabama.

It suffered another setback yesterday when a tow line snapped, setting the ship adrift once again as crews worked to repair it.

The 272-metre vessel, notorious for reports of raw sewage from overflowing toilets, has been without propulsion and running on emergency generator power since Sunday, when an engine room fire left it adrift in the Gulf of Mexico.

Operated by Carnival Cruise Lines, the flagship brand of global cruise ship giant Carnival Corp, the ship left Galveston, Texas a week ago carrying 3,143 passengers and 1,086 crew. It was supposed to return there on Monday.

Carnival Corp spokesman Vance Gulliksen in Miami said the Triumph was expected to arrive in Mobile at between 8pm and 11pm local time on Thursday night.

“This is going to be a long day,” Terry Thornton, a senior Carnival Cruise Lines vice president, told reporters at the port in Mobile.

He said the ship, which he described as “in excellent shape” after additional provisions were laid in on Wednesday, was near the sea buoy at the entrance to Mobile Bay late yesterday morning. Getting from the buoy into port normally takes about three hours, Thornton said.

“There is no way we could actually speed up the process to get the ship alongside sooner,” he said. “We’re making every effort we can to get the ship alongside here in Mobile as quickly as possible.”

A Coast Guard cutter has been escorting the Triumph on its long voyage into port since Monday. (Reuters)