KABUL, Afghanistan  Fourteen Americans were killed in Afghanistan on Monday in two crashes involving helicopters, making it one of the deadliest days in America’s eight-year war here. Neither crash appeared to involve hostile fire, American military officials said.

The American casualties occurred amid fresh tensions between Afghan politicians over a runoff presidential election scheduled for Nov. 7.

In the most lethal of the two crashes, seven American servicemen and three agents with the United States Drug Enforcement Administration died when their Chinook twin-rotor helicopter crashed in western Afghanistan after a firefight with Taliban insurgents. Twenty-six people were injured: 11 American servicemen, one American civilian and 14 Afghan soldiers.

The crash followed a gun battle with insurgents that broke out when the Americans and Afghans raided a compound believed to harbor drug traffickers. The Americans and the Afghans killed more than a dozen fighters, military officials in Kabul said. The Chinook crashed as the American and Afghan forces were leaving.