The 17-year-old youth, an office boy of businessman Rajesh Kalra whose cash was robbed, along with the three henchmen identified as Gulzar alias Bhola, Tilak alias Tinku and Praveen --all residents of Chhatarpur in south Delhi, has been apprehended, according to police.
Efforts are on to nab their other five to six associates who too have been identified by the police.
The juvenile was present in the Honda City car on Tuesday when it was looted by the assailants and was relaying live updates to the robbers about the movement of the car through text messages.
"We always believed that an insider played a key role in the biggest heist in the national capital. All those present in the car at the time of loot were under scanner and they were questioned in detail and their backgrounds were checked. As soon as the juvenile broke down, the case was cracked," said a senior police official.
The youth, a resident of Madangir in south Delhi, shared this information with his relative Ajay who has been involved in street crime in the area and they planned to loot the cash. Ajay further roped in Shakti Naidu, who is the juvenile's maternal uncle and has been involved in a number of crimes. He was also arrested in a bank robbery case in 2002.