The government may put in stringent measures to regulate the supply of ammonium-based explosives while a sophisticated fuse will be fitted to detonators supplied to the army and private contractors to prevent their use in terror attacks.

The recent blasts in Hyderabad, which claimed 42 lives, have spurred the government machinery to think of ways to regulate the sale of ammonium-based explosives that are now easily available in the market.

Major terrorist strikes in the 1990s were carried out with explosives like RDX, PETN or Semtex that can be obtained only from the military or a covert service, but ammonium nitrate-based explosives pilfered from legitimate dealers have been used for recent attacks, official sources said.

Neogel-90, a commercial explosive consisting of 90 per cent ammonium nitrate and 10 per cent emulsifier was used in the Hyderabad blasts. The probe into the attacks has indicated that the explosives were stolen from a quarry in Andhra Pradesh and purchased by terrorists from the flourishing local black market, the sources said.

The stealing of explosives is not the only area of concern as security agencies have sought a change in the design of detonators, the thin, thumb-length tubes that initiate an explosion.

The sources said the home ministry now wants detonators to be fitted with hard-wired fuses to ensure that explosions are delayed by 10 seconds after the completion of the electrical circuit.

Such fuses, the sources said, would make precision attacks on convoys of security forces or VIPs almost impossible since terrorists would not be able to set off explosions at the exact moment their targets pass by.

However, the army, which is the largest buyer of these detonators, has objected to the use of such fuses and instead suggested the introduction of a mechanism that could stop the pilferage of explosive materials.

The government had in 2004 imposed a comprehensive ban on the manufacture of nitroglycerin-based explosives for civilian purposes and replaced them with ammonium nitrate-based explosives for use in the mining and construction industries.

The idea behind bringing in ammonium nitrate-based explosives was that they easily retain moisture when left in the open and become defunct. Such explosives also have a shelf life of not more than three months.

But the ban saw the mushrooming of units making ammonium nitrate-based explosives. A total of 72 such units came up after the ban was put in place, as against three that produced explosives for civilian use till 2004.

Many factories were set up in parts of Bihar and Jharkhand, since buyers like the mining industry have a presence in these regions.

The sources said there was an urgent need to improve the system for auditing stocks of explosives and fertilizers with dual-use potential, and this would be possible only with electronic inventory management and well-secured storage facilities.

Ammonium nitrate-based explosives were used by al Qaeda in the Istanbul bombings in 2003 and the Bali attacks in 2002. European nations have already imposed strict restrictions on the sale of ammonium nitrate.