Acting on a tip-off, police from nearby Kotagiri picked up Justin Joy and Jamsher Ali, allegedly part of the gang members hired for the heist, from Mallapuram in Kerala, police said.
The two were produced before Kotagiri Magistrate C Sridhar who remanded them to three days police custody.
With this, the number of persons arrested in the April 24 incident has risen to seven.
The duo was earlier taken to the scene of the crime at Kodanadu Estate bungalow after preliminary questioning on being brought to Kotagiri in hilly Nilgiris District.
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Earlier in the day, key accused in the case Sayan was questioned by police, days after he was hospitalised after being injured in a road accident in Kerala.
District Superintendent of Police Murali Rambha interrogated Sayan alias Shyam at a private hospital in Coimbatore, where he has been undergoing treatment since April 29.
Rambha said the health condition of Sayan was stable. However, considering that he may develop unnecessary stress, he was questioned only for a few minutes, the SP told reporters.
Sayan, who was driving the car, had rammed the vehicle into a stationary truck.
Kanagaraj was killed in a road accident in Salem on the same day.
Sayan had reportedly told police that the accident involving his family occurred as he was deprived of sleep in the previous days.
As part of the investigations into the case, the Kodanadu estate workers and villagers in Kotagiri were also being questioned, police said.
The gang members had planned the dacoity based on Kanakaraj's information that there was a huge amount of cash in the bungalow, police said.
The Kodanadu estate figures in a disproportionate assets case involving jailed AIADMK general secretary V K Sasikala and late Jayalalithaa, among others.