The Mumbai Police Bomb Squad confirmed today that terrorists planted a total of five bombs in the city during Wednesday's attacks, and that at least two of the bombs used sophisticated timers unlike anything India had seen until this year.
Two of the bombs exploded Wednesday night in taxis in the north Mumbai suburb of Vile Parle and on the Mazgaon Dockyard Road in south Mumbai. The other three bombs were laid out at the entrance to the Oberoi Trident Hotel, and near the front and back entrances of the historic, now ravaged Taj Mahal Palace Hotel.
Senior Inspector Steven Anthony of the Bomb Squad told ABC News that around 10 p.m. Wednesday, he received word of a black bag abandoned at the front of the Oberoi Trident.
"There was firing going on inside the hotel," he recalled. "We used a ballistic shield on the bag and covered it, but before we could place a bomb blanket on the bag to defuse the bomb, it exploded.
"No sooner had that bomb exploded, then we got word of another very similar bag found about 30 meters [about 100 feet] from the entrance of the Taj, concealed behind a plant near the Gateway of India," he said.
Bomb-sniffing dogs were brought in to check the bag, leading the bomb disposal experts to conclude that there were explosives inside it.
"They [the attackers] had placed the bag very close to where the security forces were firing from," Anthony said.
His fellow officer, Sub Inspector Sachin Gawade, said that the bag contained a metal box, which had about 17 pounds of a greasy, black explosive inside, "very similar to the explosives found in the bombs used during the 1993 Mumbai blasts."
The material used in the bombs that hit Mumbai in 1993, killing 257 people, was RDX, which is an extremely powerful explosive that is difficult to procure inside India. Neither Gawade nor Anthony would confirm that the bombs used in last week's blasts contained RDX, saying that they were awaiting forensic tests to determine the source of the explosive.
They did say, however, that when they successfully defused the bomb found in front of the Taj they discovered ball-bearings inside, which were designed to act as shrapnel when the bomb exploded.
Around 8 a.m. Thursday, Anthony received another call, he said, this one mentioning a metal box found behind the Taj hotel, near the rear entrance.
"There was no attempt to even conceal the box," he said, noting that the bomb was "left in an area which was still very busy that morning. It was open to the public, and it was also the likely escape route for the hotel's hostages."
The box turned out to be similar to the one found near the front entrance of the Taj, he confirmed, saying that it, too, contained about 17 pounds of what appeared to be the same black substance.
More worryingly, both bombs contained sophisticated PDT timers -- programmable electronic timer-delay devices.
"Earlier bombs used in India contained mechanical, clock-type timers," Gawade said. "These timers are very advanced. You can effectively delay a bomb exploding for any length of time between eight minutes to six months.
"The only other time we have come across such timers in India is in Surat," he said.
In July, about 25 bombs were found in the western Indian city of Surat, some of which were hidden inside hoardings or placed near police outposts. "Those bombs didn't explode because of mechanical faults with the timer," Gawade said.