After interrogating the arrested — Mohammed Said, Zeeshan, Shakil, Zia-ur-Rehman and Saquib Nisar — Special Cell officials said all of them appeared to be discussing books and studies while discussing the blasts. “If they had to talk over phone about crowded places where bombs could be easily placed and they had seen the site, they would say ‘library dekh li hai, bhai’ (I have seen the library),” a source said. “If Atif was asked about the crowd and the situation at the site, his accomplice would say, ‘Main library mein kitaab padhke aa gaya hoon, aachchi hai (I have read books in the library; they are good).”

The bombs were called kitaab, or book. “When Atif procured bombs from Karnataka, he informed his superiors, including Tauqeer, over phone ‘kitabein aa gayi hain’,” the source said. “For the Delhi blasts, they used the word ‘rack’ for dustbins.

“When all of them returned after planting the bombs, they informed Atif by saying, ‘Maine rack mein kitaab rakh di hai’ (I have kept the book in the library rack).”

The codes, sources said, are the same as used in Hindi film Zameen, which is on terrorism. Atif, alias Bashir, briefed his counterparts in other states also using the code, sources said. The suspected militants used the same words when they spoke outside the flat, sources said. They used the code language to avoid interception, for the police were working on some phone numbers, the sources said.

There were more codes in the whole operation, and Special Cell officials said they are trying to crack them. Officials said numbers were also discussed in codes.