Following a spate of temple hundi robberies, police were keeping strict vigil and the two youths also came under their scanner.
It was found that the two had quit the unit after working for sometime and had bought two motorcycles, gold chains and costly mobile phones besides land, police said.
Police took them into custody and, on questioning them, found they were involved in the murder of the 58-year-old watchman and looting of Rs nine lakh from the unit.