Romania's interior minister has resigned in a growing uproar over a plane crash rescue mission that many have criticized as being too slow.

Radu Stroe handed in his notice to the prime minister Thursday to become the highest-ranking government official to leave his post. Three other officials have already resigned or been fired.

But former emergency services chief Ion Burlui, who resigned Wednesday, said authorities had done their job properly in difficult conditions including deep snow, dense fog and darkness.

The small plane, carrying a pilot and six medical workers to harvest organs for transplant, crashed on a mountain Monday. Residents located the plane 4½ hours after it crashed, but medical teams arrived much later, provoking public anger.

The pilot and a medical student died from hypothermia and multiple injuries.