Ten SIM cards were bought a month back from three different locations in Kolkata and sent to Pakistan via Bangladesh out of which three were used by Lashker-e-Taiba terrorists in the audacious Mumbai attack, investigations have revealed.

The SIM cards were purchased from Park Street and 24 Parganas (South) including Maheshtala in the name of Hossain-ur-Rahman and smuggled out of the country through Indo-Bangladesh border and then to Pakistan, official sources said.

The buyer of the pre-paid SIM cards had submitted forged election identity card as proof of residence bearing address as Bashirhat, near the Indo-Bangla border, they said, adding the agencies were trying to locate remaining seven SIM cards.

The Mumbai police and security agencies had recovered five SIM cards from the 10 terrorists involved in the November 26 attack at various places in Mumbai that left over 180 people dead and over 300 injured.

The pre-paid SIM cards -- two from Delhi and three from West Bengal -- were purchased only a month back and credited with Rs 5,000 each, the sources said.

Mohammad Ajmal Amir Iman, the lone arrested terrorist, has told interrogators that right through the strikes, the LeT headquarters in Pakistan, remained very much in touch with them, frequently calling their mobile phones via a Voice-Over-Internet Protocol (VoIP), the codes of which were being deciphered by the FBI and Scotland Yard teams, camping in Mumbai.