Federal investigators examined a new cruise ship Wednesday to try to determine why the 951-foot vessel suddenly rolled to one side, seriously injuring 20 people in a scene that looked like something out of the movie on that night's bill, "Titanic."

The Coast Guard also questioned why authorities first learned of the trouble not from the captain, but from the mother of a passenger who had called her from the ship.

The Crown Princess rolled 15 degrees to its right Tuesday afternoon about 11 1/2 miles off Port Canaveral, throwing passengers, TV sets and other objects against the deck and walls. The ship slowly came back up after 30 to 40 seconds, by passengers' estimate, then returned to port.

The crew reported a steering problem aboard the 113,000-ton vessel, which was christened only last month. The ship was sailing through calm seas, and there was no indication that a rogue wave or foul play contributed to the roll, officials said.

The Coast Guard and the National Transportation Safety Board began an investigation.

"We'll look at weather, we'll look at stability issues and we'll look at mechanical issues," Coast Guard Commander James McLaughlin said.

The International Council of Cruise Lines called the ship's listing an "uncommon occurrence."

"This incident will be closely reviewed and any changes that may be needed will be quickly implemented," the council said in a statement.

As passengers boarded buses for the airport Wednesday, many recounted the terrifying scene. Some sobbed and clutched loved ones.

"Another 20 degrees and I would have been in the water," said Alfred Caproni, of North Adams, Mass., who was on his balcony on the ninth deck. "All the water from the pools was coming right over the edge. It was like Niagara Falls. There were dozens of people with bleeding noses."

Gerald Brock, a surgeon from Ontario, Canada, said he helped ship doctors treat dozens of passengers with such injuries as broken bones, dislocated joints, short of breath and chest pains.

Tuesday night's movie aboard the ship was supposed to be "Titanic," according to several passengers.

The cruise line reported that all 3,100 passengers and 1,200 crew members were accounted for, but the Coast Guard was still verifying that information Wednesday.

"There is a possibility when you take a roll like that that somebody could have gone overboard," McLaughlin said.

About 240 passengers were treated on board for minor injuries, according to Princess Cruises. Ninety-eight people were taken to the hospital, including a child and an adult who were critically injured.

Coast Guard officials said it was unusual that first word of a problem came from a passenger's mother. The Coast Guard immediately tried to contact the vessel, but were unable to reach it for 10 minutes, Petty Officer James Judge said.

Capt. Andrew Proctor was not on the bridge at the time of the incident, Princess Cruises spokeswoman Julie Benson said. She said that she did not know who called the Coast Guard first, but that it is standard procedure for the captain to contact authorities.

Coast Guard officials said it is not uncommon for a captain to first assess the situation and ensure the ship's stability before contacting them.

Investigators said there was no indication the captain was under the influence of drugs or alcohol. He tested negative for alcohol; drug test results were still pending.

"He's one of our most senior captains. He's been with the company for about 35 years. He has an exemplary record," Benson said.

She said all passengers on the nine-day Western Caribbean cruise ending in New York would receive a full refund.

A similar incident occurred in February on a ship also operated by Princess. The 2,600-passenger Grand Princess left the Port of Galveston but soon turned around after a passenger suffered a heart attack. The ship tipped sharply on its side, injuring 27 passengers and 10 crew members. The incident was blamed on human error, Benson said.

James Hall, former chairman of the NTSB, said Wednesday he hopes the latest incident will prompt federal officials to toughen cruise industry regulations.

"This was a serious roll, there were injuries and obviously the people that were on the ship were terrified," Hall said.