Anam Sheikh, whose father Aejaz Ahmad was killed in the Mumbai blasts

Mumbai, July 17: The powerful and difficult-to-access RDX and the locally available ammonium nitrate were both used in the July 11 train blasts, forensic tests have revealed.

The bombs were set off with timers, traces of which were found in the samples collected by police, anti-terrorist squad chief K.P. Raghuvanshi said today. Lubrication oil that creates black smoke and could have choked blast survivors and triggered a stampede has also been found.

At least two of the seven blasts were set off with RDX and the rest with ammonium nitrate-filled gelatin sticks, Raghuvanshi said. “The blasts are the handiwork of people from across the border.”

RDX isn’t made anywhere outside full state control, and therefore suggests a foreign hand. It’s strongly associated with the Lashkar-e-Toiba which reportedly has links with the Pakistan army and the Inter-Services Intelligence.

In Mumbai, however, it’s easy to get glass tubes filled with a brownish gel ? a mix of ammonium nitrate, nitro-glycerine, sodium nitrate and fuel oil -- locally known as gelatin sticks, each costing Rs 50. Ammonium nitrate is a fertiliser and can be separately bought at agricultural supply stores.

The forensic experts took so long because the sample size (collected from rain-washed tracks and compartments) was small, Raghuvanshi said. The police had approached the Central Forensic Science Laboratory in Hyderabad, the bomb unit of the National Security Guards, the Bomb Data Centre in New Delhi and Mumbai’s Kalina-based State Forensic Laboratory.

“We wanted to be doubly sure and waited to see if all of them produced the same reports,” an officer said.

Raghuvanshi said “encounter specialists” Vijay Salaskar and Daya Nayak ? in judicial custody on corruption charges ? would be drafted in to help with the probe.

He denied reports that two persons had been arrested in Madhya Pradesh and another two, held in Nepal, had been brought to Mumbai.

A team has left to question 11 visitors from Thane held in Tripura’s border areas. “If it’s found they have knowledge of any pre-blast or post- blast developments, they will be brought to Mumbai,” Raghuvanshi said. Also under the scanner is a UK-based website.