Portuguese authorities have also confirmed that 336 cases have been identified in total since the outbreak began on November 7. Of these, 38 remain in a serious condition in intensive care, with 23 currently receiving ventilatory support.
The 10 deaths – seven men and three women – ranged in age from 52 to 89.
The Portuguese health ministry says it is confident it has identified one source which emitted a legionella aerosol.
Prosecutors are to investigate a possible breach of environmental legislation originating
from the wet cooling systems of the Adubos de Portugal fertiliser factory.