A cargo door blew off a United Airlines jet with 354 people aboard early Friday, ripping a 10-by-40-foot hole in the fuselage at 22,000 feet, hurling as many as 11 people to their deaths and injuring at least 17.

The flight, bound for New Zealand and Australia, made it back to Honolulu. Rescue ships and aircraft were sent to search the Pacific in the area where the plane turned back.Passengers described hearing an explosion and investigators tried to determine if a bomb or structural failure on the 18-year-old Boeing 747 were involved.

Law enforcement sources in Washington said an initial examination indicated that "there was a big hole but it was not an explosive tear in appearance."

Passenger Gary Garber said some people were "blown out" of the plane.

"There was an explosion on the plane, in the business section, probably right above the cargo area," he told CBS News. "We were in the center section of the plane and the people at the aisle section - about four, six of them, whatever - were blown out of the plane and I presume they're lost."

Another passenger, Beverly Nisbet, 50, who was on her way home with her daughter to Hastings, New Zealand, said she "noticed a slight change in the engine sound and almost at the same moment there was the explosion. I believe some people were sucked out but I don't really know."

"We all quickly put on our life vests and just stayed belted and silently prayed," she said. There was "a bit of panic" among the passengers. "We all thought our time had come."

The blast caused the interior wall to blow into the plane, she said, and there was "debris flying around."

"One girl was screaming a lot," Nisbet said. "One very brave man picked her up, took her to the back of the plane and calmed her down."

Flight 811 was less than 20 minutes into its flight to Auckland, New Zealand, when the pilot reported a loss of power in one of his four engines.

He managed to land the crippled plane, which carried 336 passengers and a crew of 18, at 2:33 a.m. local time at International Airport, where passengers were evacuated.

As the jetliner made its emergency landing, power was lost in the No. 4 engine, leaving only the two engines on the left wing functioning.

State Transportation Department spokeswoman Marilyn Kali said the first engine was apparently lost when the blast knocked off the right front cargo door.

"The captain and the crew did a superb job of returning the aircraft," United Airlines said in a statement issued in Chicago.

Kali said about a dozen people, some suffering broken arms and legs, were taken to Honolulu hospitals. "Many of (the injuries) may have been suffered (as passengers used) the exits down the chute," she said.

Passenger Bruce Lampert of Denver said, "There was explosive decompression. The masks came down. There was a lot of debris flowing through the cabin.

"I heard a large rushing of noise. The plane made a rapid descent. I can tell you that was a long flight back," he said. When passengers saw land "there was a roar of applause," he said.

"The passengers were wonderful; the crew as professional. There was an awful lot of scared people, obviously," Lampert said. He said he saw one woman with a severe neck cut, bleeding all over her blouse.

At Honolulu International Airport, United Airlines took a head count among the passengers, who were quickly moved off the plane after it made a safe landing.

The passengers were told to remain in the area at the terminal's gates 9 and 10, and were told not to leave.

Many of the passengers were lying on the floor, with blankets and pillows provided by United. One passenger was still wearing his life jacket.

FAA spokeswoman Theresa Greco in Washington said the pilot radioed air traffic controllers after losing power in the No. 3 engine and, after declaring an on-board emergency, descended to 4,400 feet.

Flight 811 originated in San Francisco and stopped to pick up passengers in Los Angeles. Authorities there also were investigating to determine if the cause of the explosion could be traced back to Los Angeles.

The last major aviation incident in the Honolulu area occurred April 28, 1988, when the top of an Aloha Airlines Boeing 737 blew away at 24,000 feet. A flight attendant was sucked out of the plane and killed. The aircraft landed 15 minutes later at Kahului Airport on Maui.

The cause of that accident appeared to be metal fatigue.