Indian police have arrested two men in the eastern city of Kolkata suspected of supplying the Mumbai attackers with mobile phone cards.
The deputy commissioner of detectives in Kolkata, told Reuters the two men - identified as Tausif Rehman and Sheikh Mukhtar -- were being questioned "about procurement of Sim cards used in Mumbai".
At least 170 people died in the attacks last week in which gunmen struck two luxury hotels, a railway station and other landmarks across India's financial capital.
Nine of the 10 militants believed to have mounted the attack were also killed, and the 10th suspect is in custody.
India has blamed Pakistan-based militants for the attacks but Islamabad denies any role.
Reuters news agency says if the men are involved, it will be further evidence of Indian complicity in the three-day rampage Delhi has blamed on Islamic militants from neighbouring Pakistan.
In February police arrested an Indian citizen, Faim Ansari, who was carrying maps of Mumbai that highlighted several of the targets later hit in the attack.
Airports in Delhi, Bangalore and Chennai remained on high alert for a fourth day on Saturday, with extra security personnel deployed after India's civil aviation authority said it had received intelligence that attacks could be planned.
Police were expected to give a fuller statement on the arrests later on Saturday.