Kabul, Afghanistan ? The 30 American service members — most of them elite Navy SEALs — who died when their helicopter was shot down had rushed to help Army Rangers who had come under fire, two U.S. officials said Sunday.

The heavy loss shows that clandestine tactics carry huge risks despite the huge success of the SEAL mission that killed Osama bin Laden more than three months ago. Most of the SEALs who died Saturday were from the same unit that killed bin Laden, although none of the men took part in that mission.

The U.S.-led coalition plans to rely more on special operations missions as it reduces the overall number of combat troops by the end of 2014.

This weekend, the rescue team had subdued attackers who had pinned down the Rangers and were departing in their Chinook helicopter when the aircraft was apparently hit, one of the officials said.

Thirty Americans and eight Afghans were killed in the crash, making it the deadliest single loss for U.S. forces in the decade-long war in Afghanistan. The Rangers, special operations forces who work regularly with the SEALs, secured the crash site in the Tangi Joy Zarin area of Wardak province, about 60 miles southwest of Kabul, the other official said.

Both officials spoke on condition of anonymity to describe the event, as the investigation is still ongoing. The SEAL mission was first reported by CNN.

NATO was recovering the remains of the twin rotor Chinook helicopter. A current and a former U.S. official said the Americans included 22 SEALs, three Air Force combat controllers and a dog handler and his dog. The two spoke on condition of anonymity because military officials were still notifying the families of the dead.

All but two of the SEALs were from SEAL Team 6, the unit that killed bin Laden, U.S. officials said on condition of anonymity because they were not authorized to release the information.

Eight Taliban fighters were also killed in the battle, Taliban spokesman Zabiullah Mujahid said in a statement.

Afghanistan has more U.S. special operations troops, about 10,000, than any other theater of war. The forces, often joined by Afghan troops, are among the most effective weapons in the coalition’s arsenal, conducting surveillance, infiltration and capture missions and night raids.

From April to July this year, 2,832 special operations raids captured 2,941 insurgents and killed 834, twice as many as during the same time period last year, according to NATO.