Rashid and Shahid were arrested from Haryana's Mewat region last December in connection with a case of planning to carry out terror attacks in Delhi and adjoining areas.
Special Cell of Delhi Police moved an application before Additional Sessions Judge Daya Prakash, saying they require 15 days to complete the probe as missing links in the conspiracy would be established once Subhan, who was allegedly in touch with Pakistan-based top LeT terrorist Javed Baluchi, was arrested.
It said that names of two more suspects, Javed and Sabbir, have also surfaced during the investigation and they were also absconding.
The probe agency also claimed that Rashid and Subhan were in touch with Baluchi through mobile phone numbers and, according to reports of a central intelligence agency, Baluchi is a "known terrorist".
The court allowed the plea of the Special Cell and granted it time till April 23 to conclude its investigation.