There seems to be some confusion as to the materials used in the improvised explosive devices (IEDs) that killed more than 200 people on the commuter rail system in Mumbai, India, on July 11. Indian authorities first said the explosive RDX was the primary material, and then said it was either a mixture of ammonium nitrate (AN) and gelatin, or RDX and gelatin. Finally, they settled on a combination of RDX and AN mixed with fuel oil, or ANFO. That conclusion, however, seems a bit odd. Further adding to the mystery surrounding the case is the Indian government's apparent inability to identify and arrest the cell responsible for the attacks — a state of affairs that also adds to fears that more attacks will follow. The problem with the Indians' conclusion is this: Although it is not unusual for bombmakers to use RDX or something like it as a booster to make an IED containing ANFO explode, improvised ANFO mixtures generally do not work well in small IEDs, like the ones used July 11. Hence, it is unusual to see them employed in such a way. The RDX booster alone likely would have caused almost as much damage as a small quantity of an improvised ANFO mixture. Therefore, if AN indeed were used in the attack it probably was not in an improvised mixture, but in the form of a commercially manufactured AN dynamite or one of the many types of AN blasting compounds. The use of AN dynamite also could help to explain the initial conflicting reports of "gelatin" and RDX. AN dynamite and blasting agents have largely replaced gelatin and nitroglycerin dynamite in many parts of the world — especially in mining-type applications. In the vernacular used by Indian authorities, it would not be surprising for them to refer to AN dynamite or a soft pack of AN blasting agent as "gelatin." The problems with identifying the materials could have been exacerbated by the forensic techniques and facilities used in the investigation. After the bombings, the Indians quickly cleaned up the bomb sites — removing the shattered rail cars, sweeping up debris and hosing the areas down. This practice is fairly common in many countries as authorities rush to return the city to a sense of normalcy. Mumbai's Western line was operational again within hours, and was ready for the next morning's commuter rush hour. By doing this, the Indians might have discarded or destroyed crucial evidence in the attack, such as small bits of unexploded explosive compound and explosive residue — the chemicals produced when an explosive compound detonates. In many countries laboratory conditions are not carefully controlled, meaning materials recovered from one blast site can be contaminated by traces of other explosive compounds and residue left in the laboratory from earlier tests. This, of course, makes valid test results difficult to obtain. In this case, the confusion probably was compounded by the bombmaker's use of different materials in the devices — likely as a result of having a variety of explosives on hand. For example, he could have constructed one device of RDX, a second out of AN dynamite and a third out of a combination of the two, so samples taken from different scenes could provide conflicting test results. That investigators recovered one unexploded device, and still took so long to release their definitive conclusion, also suggests various materials were used. Indian authorities have issued a warning for Mumbai, saying more attacks by the same cell are possible. This is because the Mumbai bombings were not carried out by suicide bombers, meaning they have lived to bomb again. Although the Indians have rounded up a large number of people in connection with attack, only one person has been detained for questioning. This suggests the bombers, their leaders and the bombmaker remain at large. It might not take them long to regroup and prepare another attack. The warning has raised concerns among the multinational corporations operating in Mumbai and India's high-tech corridor, which includes Bangalore, Pune and Hyderabad. The attackers, however, successfully hit a soft target — and are likely to try the same thing again. Escalation would be switching to banking or other financial targets, though in general those facilities are better protected.