* Company says some toilets working
* "Condiment burgers" and cold onion sandwiches for dinner
* Plastic 'biohazard' bags serve as improvised toilets
More than 4,220 people on the stricken cruise ship Carnival Triumph faced another night of what some have described as hellish conditions on Wednesday, as the company said it was offering passengers an additional $500 in compensation for their hardship.
The 893-foot (272 meter) vessel has been without propulsion and running on emergency generator power since Sunday, when an engine room fire left it adrift off Mexico's southern Yucatan Peninsula. It is being hauled by tugboats to Mobile, Alabama, where it is due to arrive no later than Thursday.
The ship's is operated by Carnival Cruise Lines, the flagship brand of Miami-based Carnival Corp, the global cruise industry giant.
Earlier this week, some passengers who contacted relatives and media before their cellphone batteries died reported a horrific situation, saying the ship was awash in raw sewage from overflowing toilets and running short on food and water.
Kim McKerreghan told television news network CNN that her husband and young daughter said in a call from aboard the ship on Monday that passengers were being forced to defecate in plastic bags due to a shortage of working toilets and that meals consisted of sandwiches with only condiments or onions.
Nick Ware, whose mother is among the Triumph passengers, told the network, "Once the meat for the burgers ran out, they were basically just eating condiment hamburgers. Just, you know, whatever condiments they could get on a bun."
He said some passengers had been instructed to use "red biohazard bags" as makeshift toilets on Monday.
The ship left Galveston, Texas, last Thursday carrying 3,143 passengers and 1,086 crew and had been due to return there on Monday.
Carnival Corp spokesman Vance Gulliksen has stopped short of denying some of the more alarming reports about conditions aboard the Triumph. But he told Reuters on Wednesday that a technical team on board had succeeded in gradually restoring auxiliary power to operate some basic hotel functions.
"Public and cabin toilets are operational in certain sections of the ship and some power in the Lido dining area is providing for hot coffee and limited hot food service," he said.
He did not elaborate on the number of working toilets for the 4,229 people but said the ship had cold running water and that three Carnival ships had rendezvoused with the Triumph to provide additional supplies and meals.
On Tuesday, the U.S. National Transportation Safety Board said it had launched an investigation into the cause of the Triumph fire. But it said the Bahamas Maritime Authority was the primary investigative agency, since the ship was a Bahamian flagged vessel.
Carnival Cruise Lines had already said passengers would receive a full credit for the cruise plus transportation expenses and a future cruise credit equal to the amount paid for the Triumph voyage.
In a statement late on Wednesday, Carnival Cruise Lines President and Chief Executive Gerry Cahill said the company had decided to add further payment of $500 per person to help compensate passengers for "very challenging circumstances" aboard the ship.
"We are very sorry for what our guests have had to endure," Cahill said.
The troubles on the Carnival Triumph occurred a little more than a year after 32 people were killed when the Costa Concordia, a luxury cruise ship operated by Carnival's Costa Cruises brand, was grounded on rocks off the Tuscan island of Giglio in Italy.
Shares in Miami-based Carnival closed down 4 percent at $37.46 Wednesday on the New York Stock Exchange after the company said voyage disruptions and repair costs related to the Carnival Triumph could shave as much as 10 cents per share off its second-half earnings.