The Delhi Police said they will seek his further remand.
A Delhi court sent Tunda to three-day police custody on Saturday.
The Delhi Police have revealed that Tunda was in direct contact with the former Inter-Services Intelligence Agency (ISI) chief of Pakistan, reports said.
The Delhi Police sources claimed that Tunda told interrogators that he met former ISI chief Hamid Gul in 1995.
Tunda said since 1995 he had been in regular touch with him.
Gul, who retired in 1992 as chief of the ISI, has however, refuted this allegation.
Speaking to NDTV, Gul said, "He (Tunda) is lying. There is no truth in his claims. I have never met him."
The Special Cell of Delhi Police on Saturday said they have arrested Tunda from the Indo-Nepal border.
The police said Tunda trained Muslim youths to make improvised explosive devices (IEDs).
The 70-year-old is wanted in India for 40 terror and 33 criminal cases.
Tunda, who masterminded 40 blasts in New Delhi, Panipat, Sonepat, Ludhiana, Kanpur and Varanasi between December 1996 and January 1998, killed 21 people and injured over 400 others.
"He also played a role in blasts in Mumbai and Hyderabad in 1993," Delhi Police Special Cell commissioner SN Srivastava had said. "In 1996, he came back to India via the Dhaka youth."
"There were serial blasts in Delhi just after that and he was responsible for it. He was associated with Hafiz Saeed and Zaki-ur-Rehman Lakhvi," said the cop.
Tunda was a resident of Pilkhuwa city of Uttar Pradesh.
--IBNS (Posted on 20-08-2013)