The Bangladesh Meteorological Department recorded 508 millimetres (1.6 feet) of rain in Rangamati alone over the past two days.
The mudslides swept over thatched homes and settlements and telephone and transport links have also been cut off.
The death toll in affected areas is expected to increase as there are many people still reported as missing.
Concern has been fighting extreme poverty in Bangladesh for 45 years and today has 55 staff working with local partner organisations in the country located between Burma and India in the Bay of Bengal.
Bangladesh is just over twice the size of the island of Ireland with a population that is over 25 times larger in what is one of the most densely populated countries in the world.