SYDNEY, Australia - Rescuers returned to treacherous seas Thursday to hunt for possible survivors after a wooden boat smuggling up to 100 asylum-seekers smashed against the cliffs of an Australian island, tossing passengers overboard and killing at least 28.

The passengers included people of Iraqi, Iranian, and Kurdish origin, Prime Minister Julia Gillard said.

The deaths at remote Christmas Island underscored dangers faced by hundreds of refugees who have tried to sail from Indonesia to Australia in recent years - often in cramped, barely seaworthy boats - to start new lives after escaping from poor, war-ravaged countries.

Navy and customs officers on the island pulled 44 people, including 11 children, from raging surf in the hours after the boat was battered to pieces on limestone rocks, but dozens of others were missing. Immigration Minister Chris Bowen said that up to 100 people may have been aboard, though the true number might never be known.

Sea conditions were dangerous, with a cyclone hovering northwest of the island, which is the 52-square-mile tip of a dormant volcano poking out of the Indian Ocean 1,600 miles from the Australian mainland.

A local hospital treated more than two dozen injured, and authorities transported two women with the worst injuries to Perth in mainland Australia for treatment. A victim identification team was arriving Thursday.

The Royal Flying Doctor Service sent doctors to the island to treat the injured, spokeswoman Joeley Pettit-Scott said. Blunt trauma was common among the victims, many of whom were battered by debris as they clung desperately to the remains of the sinking boat.

Christmas Island residents watched helplessly from a high cliff Wednesday morning as the boat struggled in the monstrous waves and then crashed, dumping screaming men, women, and children into the stormy surf.

"It was just horrible," island resident Simon Prince said. "People getting crushed. Bodies, dead children, the whole thing was pretty awful."

Christmas Island is closer to Indonesia than to the Australian mainland and is a frequent target of refugee hopefuls, who are housed in a detention center there.

In recent years, many asylum-seekers have come from Afghanistan, Iran, Iraq, and Myanmar. Generally, they first fly to Indonesia and then continue on to Australia by sea, often in small, rickety fishing boats with few provisions and no safety gear.

Australian authorities acting on intelligence usually track larger asylum-seeker boats after they leave Indonesia and often intercept them when they reach Australian waters. But some are too small to appear on radar and may not be spotted until they are very close to land.

The boat appeared near the shore very early Wednesday morning in bad weather that hampered visibility.

Photos and video from witnesses showed the boat crashing into jagged rocks and breaking apart, as well as people floating in the water.