U.S. military officials say the death toll from Wednesday's helicopter crash in southeastern Afghanistan has risen to 16, including at least four American crew members.

A U.S. statement says two other people listed on the flight manifest are missing.

The Chinook helicopter was returning to Bagram air base from Ghazni province, southwest of the capital, Kabul, when it went down near Ghazni city.

The U.S. military suggests severe weather was to blame for what is the deadliest military crash in Afghanistan since the start of U.S.- led operations to oust the Taleban in late 2001.