Irish charity Goal has said 26 of its workers have been confirmed dead, following a massive earthquake in Turkey and Syria on Monday.
The humanitarian organisation has long-term operations in southern Turkey and north-west Syria.
More than 20,500 people are now confirmed to have died in the 7.8 magnitude quake.
The total number who are recorded as having been killed is at least 20,511 - including 17,134 in Turkey and 3,377 in neighbouring Syria.
The crucial 72-hour window - in which people are most likely to be found alive - has passed.
Goal said teams are still working 'around the clock' to account for a number of staff still unaccounted for, while also supporting the overall search and rescue mission.
'Profoundly difficult week'
Goal CEO Siobhan Walsh said it has been a very difficult time.
"To say it has been a profoundly difficult week for the Goal teams in Turkey and Syria cannot be overstated," she said.
"Because of the sheer geography of destruction, and Goal's long-term presence in the communities so severely impacted, the scale of loss is far beyond anything we could have ever imagined.
"Goal staff across the region have also lost family members, sustained life-altering injuries and lost their homes.
"Teams in Turkey and Syria have mobilised responses to assess needs on the ground, whilst prioritising the immediate restarting of key humanitarian aid programmes that deliver shelter, access to food, clean water and health and social support."
Ms Walsh said Goal's global team across 14 countries are "united as one as they support their heartbroken colleagues in Turkey and Syria."
"Never in the organisation’s history has Goal experienced the loss of colleagues on such a scale," she added.
'The ultimate price'
Tánaiste and Foreign Affairs Minister Micheál Martin has offered his condolences to staff.
"I was deeply saddened to hear of the significant loss of life among Goal staff as a result of Monday's tragic earthquake," he said.
"The Goal staff members who lost their lives were carrying out vital humanitarian work to support the people of north-west Syria, who have suffered unimaginably over recent years.
"Humanitarian workers put their own lives at-risk to support the most vulnerable people in the world.
"Too often, they pay the ultimate price.
"I want to offer my sincere condolences to the families of those who lost their lives, as well as to all the Goal teams around the world for whom this will come as a devastating blow.
"The staff members who died dedicated their lives to supporting people in need of humanitarian care.
"Each of them leaves a legacy of kindness, compassion and humanity," he added.
