The Saudi-led Arab Coalition Forces Command backing Yemen’s legitimate government announced on Tuesday morning a Saudi Black Hawk helicopter crashed while on a mission in Marib.

The Saudi Black Hawk “fell during operations in the province of Marib” east of Sanaa, the coalition said in a statement carried by SPA state news agency.

Coalition spokesman General Ahmed Assiri told AFP it was “too early” to comment on the causes of the crash, which is one of the deadliest incidents involving coalition forces in Yemen. The investigations are ongoing to determine the causes of the accident.

A Saudi-led coalition began air strikes over Yemen in March 2015 in support of President Abedrabbo Mansour Hadi’s internationally recognized government in its fight against Iran-backed Houthi rebels.

Seven ceasefires brokered between government and rebel forces by the United Nations have failed, while UN-backed peace talks have repeatedly broken down.