BANDA ACEH, Indonesia - A U.S. helicopter on a relief mission crashed in a rice paddy 500 yards from the Banda Aceh airport today, injuring two servicemen. Schools opened for the first time since the Dec. 26 tsunami, but many of the 150,000 lives the epic waves claimed were children, and thousands of desks sat empty.

Workers, meanwhile, struggled to recover 50,000 bodies the government said were "scattered" throughout the region.

The U.S. military said the Seahawk helicopter "executed a hard landing" and that there was no evidence it was shot down near the airport in Banda Aceh, capital of Indonesia's hard-hit Aceh province and the hub of international aid operations. Lt. Cmdr. John M. Daniels blamed the crash on a "possible mechanical failure."

He said one person fractured an ankle and the other dislocated his hip. The other eight suffered "no significant injuries," he said.

Fifteen Seahawk helicopters from the Lincoln group have been flying up to nine hours a day on aid missions. Normally they fly a maximum of three to four hours a day.

The crash came amid heightened security concerns in several tsunami-hit areas with ethnic rebellions - particularly in Aceh, where rebels have waged a separatist war in the province for nearly three decades. United Nations staff in Aceh are on high alert, and armed guards patrol their compounds amid fears of rebel attacks.

Aftershocks from the massive earthquake that spawned the killer waves continued to rattle residents in the hardest-hit countries. A 6.2-magnitude temblor sent people scrambling from their homes early today in Banda Aceh; no injuries or damage were reported.

In the latest sign life is slowly returning to normal, children returned to school in Indonesia and Sri Lanka for the start of the new term - long before many institutions damaged in the disaster can provide proper education. Social workers hope the resumption of studies will help children overcome the trauma of the catastrophe.

In a rare happy story, a 22-year-old Indonesian, Ari Afrizal, was rescued at sea sometime late last week by the United Arab Emirates-registered AL Yamamah, said Sasheila Paramsothy, a spokeswoman for the shipping harbor Westport Malaysia.

Ari was swept out to sea when the tsunami hit his home in Aceh, Paramsothy said, adding that the ship crew has not provided other details.

A senior Navy officer involved in the humanitarian aid mission said the U.S. military is likely to remain in tsunami-devastated areas for an extended period.

"I don't see an end to this for a long, long time," Capt. Larry Burt said of the American presence on Sumatra island. Burt is the commander of the air wing aboard the aircraft carrier USS Abraham Lincoln.

Indonesia's military warned aid workers Sunday that rebels in Aceh were taking shelter in camps for survivors, but the government dismissed those claims today. The government also said rebels were not responsible for a shooting near the main U.N. compound on Sunday, contradicting earlier assertions by the country's military and police.