Karat, who headed a party delegation and submitted a memorandum to Das, demanded the probe into the killing of a 32-year-old man and a 13-year-old boy and government jobs to the deceased's wife and one of the parents of the boy.
A copy of the memorandum was later released to the press.
Karat had yesterday met the family members of the deceased in Latehar.
Five of the eight persons allegedly involved in the killings in Jhabbar village were arrested on March 19. The other three gave themselves up in a local court during the day and were remanded to 14 days in judicial custody.