A National Guard helicopter carrying Border Patrol agents to search a remote mountain area for human smugglers crashed a few miles from the Mexico border, injuring the nine people aboard.

The five agents and four National Guard members were hospitalized, but none had life-threatening injuries, officials said.

"To have a bird go down like this with nine people on board and not have anyone in intensive care is a huge relief," said James Jacques, a Border Patrol spokesman in San Diego.

The UH-1, one of the older models used by the National Guard, crashed Tuesday afternoon about 20 miles southeast of downtown San Diego, said National Guard Master Sgt. Michael Drake.

It came to rest on its belly, its top rotor snapped off and what appeared to be its tail thrust to its side.

Authorities declined to discuss a possible cause of the crash, and Guard officials would not comment on either the pilot's training or the helicopter's maintenance history. Department of Forestry Capt. Brennan Blue said power lines were down near the crash site, "but it's undetermined whether they went down before the crash or after."

The skies were clear in the area Tuesday, though a wind advisory was posted for the area's mountains, the National Weather Service said.

The UH-1 was on a mission for Operation Jumpstart, which stemmed from President George W. Bush's plan to deploy up to 6,000 National Guard troops along the U.S.-Mexico border for about two years to help local and federal law enforcement stop illegal immigration.

The crash was the first since the operation started there in July, said National Guard Capt. Mike Morgan.

At least 100 such missions have been conducted and are "relatively safe" with weather usually being the major concern, Morgan said.

About 1,400 Guard members currently patrol the California-Mexico border, officials said.