According to local media reports that originally surfaced in Pakistan last month, Riaz was remanded for interrogation.
Islamabad admitted in February for the first time that the Mumbai attacks were planned partly in Pakistan and filed a case against eight suspects, saying that six of them were already in custody.
"We have written to the foreign office today to request India for some more information," Malik said.
Back and forth
India in January sent Pakistan a dossier, which it said contained evidence that elements in Pakistan were behind the November attack.
In February, Pakistan sent another 30 questions, to which India responded in March.
The Indian deputy high commissioner in Islamabad was called to the interior ministry on Monday to be briefed on "missing information and what is our requirement", Malik said.
He said Pakistan asked India to urgently provide a certified copy of the statement given by Ajmal Kasab, the alleged lone surviving attacker, before a magistrate.
He said Pakistan also requested that India provide a copy of the charge-sheet against Kasab, 21, who is also known as Ajmal Iman.
Kasab's trial is due to start in Mumbai on Wednesday. He faces the death penalty if convicted on a string of charges relating to the Mumbai attack.
Samples in question
Malik also questioned the DNA samples that Indian authorities have provided.
"One sample is of a terrorist named Ismail, who was killed during the operation, which is identical to the sample of Kasab", Malik said.
"We also do not have details about the SIM cards used by the attackers, the co-ordinates for the GPS and information about the Indian nationals arrested for involvement in the attack.
"We need this information as urgently as possible for successful prosecution."