The apartment buildings after the crash
The Bijlmer Disaster happened when El Al Flight 1862, a Boeing 747 cargo aircraft of the state-owned Israeli airline El Al, en route from New York via Amsterdam to Tel Aviv, crashed into residential flats in the Bijlmermeer (colloquially "Bijlmer") neighbourhood in Amsterdam, the Netherlands, killing at least 47 crew and residents, and creating massive health problems for several thousand survivors on the ground.
On September 30, 1998, editors Harm van den Berg and Karel Knip of the prestigious Dutch daily NRC Handelsblad provided their readers with incontrovertible documentation that LY1862 was transporting three of the four components required for the manufacture of Sarin nerve gas.
According to freight documents uncovered by NRC Handelsblad, LY1862 was carrying 10 18.9-litre plastic drums of dimethyl methylphosphonate (DMMP), and smaller amounts of the Sarin precursors isopropanol and hydrogen fluoride (no revelations have been made regarding the remaining precursor, thionylchloride). The 189 litres of DMMP, sufficient for the production of 270 kg of Sarin.
The Amsterdam engineering firm Omegam, which investigated the crash site, discovered extensive traces of tributylphosphate (TBP) and concluded that at least several hundred litres of the liquid must have been aboard. Yet TBP, a fairly common industrial chemical which can also be employed to recycle uranium and plutonium from spent fuel rods in a process Mordechai Vanunu revealed is used in Israel, appears nowhere in LY1862's freight documents. 
The Cover Up
On account of Israeli stonewalling and disinformation, and a campaign of obfuscation by the Dutch government and law enforcement agencies, they have produced more questions than answers. Among questions still to be answered are why neither of LY1862's flight data recorders (black boxes) have yet to surface, and the matter of two groups of "men in white suits" immediately and several hours after the disaster that were witnessed in sworn affidavits by Bijlmermeer residents, emergency crew members and law enforcement personnel. They were said to be wearing thick protective clothing (one group was likened to "astronauts"), which permitted them to "walk through the flames unaffected" and disappear with various pieces of debris.
The witness accounts states that the second group of men in white suits arrived in vehicles bearing French licence plates, raising the possibility that operatives from Mossad's European headquarters in Paris were involved in the removal of evidence. Staff attached to the Mossad station at Schiphol airport, and covert Dutch (or NATO) military emergency units, may also be shown to have been involved if the allegations are ever seriously investigated.
Another aspect requiring clarification concerns the multiple and contradictory freight documents supplied to Dutch authorities. A Dutch TV program from 1998 featured statements by former El Al employees at Frankfurt airport and elsewhere that they regularly tampered with such documents on behalf of their superiors.
There is considerable evidence that the Dutch government at the time, led by PM Wim Kok (and particularly the ministry of transport) at various points held back, and subsequently failed to make known the significance of, technical and other information in its possession.