Two workmen from Bihar were among the deceased.
The deceased were identified as Harnad Verman (27), Bhajan Verman (20), both hailing from Bihar, and Unnikrishnan (26).
Another body is yet to be identified, hospital sources said.
Five persons were at the flat construction work site at Panganpara when a nearly ten-foot mound of earth from a slope crashed down on the workers when the work on a compound wall was progressing.
One person was rescued from th debris by fire force and police personnel, police said.
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Several parts of the state are experiencing heavy rain in the last two days.
State Minister Kadakampally Surendran said realtors carried out the construction without taking any precaution.
Earth in that area was very loose due to the rain during the last two days, he said.