The United Nations said on Tuesday that one of its staff members had died in detention in northern Yemen, where the U.N. has repeatedly called for the Houthi movement to free detained U.N. employees.

The United Nations said Monday it suspended its humanitarian operations in the stronghold of Yemen’s Houthi rebels after they detained eight more U.N. staffers, affecting the global response to one of the world’s worst humanitarian disasters.

The total employees arrested since 2021 has risen to 24, a U.N. spokesman said. The Iran-backed Houthis have held them on murky charges of espionage and foreign intervention.