Meanwhile, Al-Arabiya TV reported Monday that it received a claim of responsibility for the attack by a previously unknown group called "The Fedayeen of Islam," but noted that it could not authenticate the audio recording or the name of the group.
According to the recording, the group said 250 U.S. Marines and other U.S. and NATO officials were inside the hotel at the time of the attack.
It said the group regretted the attack, but said it was necessary to press its demands, including an end to U.S.-Pakistani joint efforts and a halt to all military operations in Pakistan's tribal regions.
No arrests have been made in connection with the attack. But Malik said suspicion was falling on militants in Pakistan's tribal regions.
"I am not in a position to tell you who has done it, but (in) all the previous investigations, all the roads have gone to South Waziristan," he said.
South Waziristan is one of seven agencies of Pakistan's tribal areas where Taliban and al Qaeda militants are active.
Saturday's massive blast left a nearly 18-meter-wide (60 foot) crater, which was 7m deep (24 feet). It also caused a natural gas leak that set the top floor of the five-story, 258-room hotel on fire, police said. The blaze quickly engulfed the entire structure. At least 57 people were killed.
The blast occurred about 7:50 p.m., after the breaking of the fast during the holy month of Ramadan.