"We are working on three aspects of recent intercepts and the passage of Hizbul Mujahideen cadres into Delhi, possibly a week before this attack," a police source told PTI.

Hizb commander Abu Rasheed went from Srinagar to Jammu on February 12. He later disappeared from Jammu and possibly went to Delhi or Haryana a few days before Sunday's attack, sources said.

Rasheed was carrying arms and explosives with him, they said. Security agencies are also working on an intercept in which two Lashker-e-Tayiba commanders talked of meeting to execute some plan.

One commander told the other to prepare some things and keep them ready, the sources said.

These two commanders spoke over the mobile phone of a Delhi-based person who is being tracked, they said. The third aspect of the probe relates to the information that another top commander would reach Delhi from Pakistan and that he should be immediately shifted from the national capital to Kashmir, they said.

All the intercepts were made just before Sunday's attack on the Samjhauta Express. Though they were not specific, they are being looked into seriously, the sources said.