( CNN ) -- The alleged terror incident aboard a passenger flight from Amsterdam to Detroit has raised questions as to how a Nigerian man carried explosives through stringent security measures . Umar Farouk Abdulmutallab has been charged with attempting to destroy a passenger plane after he detonated a device on board a jet on Friday . Authorities in the United States are investigating whether Abdulmutallab had any connections with terrorist organizations or was acting alone . Airports intensify security after plane attack . With Dutch officials scrutinizing security procedures at Amsterdam 's Schiphol airport that allowed the 23-year-old man to smuggle the explosives on the aircraft -- here are some of the key questions still hanging over the incident . Where did the explosives come from ? The man charged with igniting the device claims he obtained the explosives in Yemen , along with instruction on how to use it . He carried these onto a flight from Lagos , Nigeria , to Amsterdam , Netherlands where he transferred to Northwest Flight 253 to Detroit . Was he on any security watch lists ? U.S. authorities say they were contacted by the man 's father ahead of the attack , but whether he was placed on any so-called No-Fly list maintained by the United States is unclear . Dutch officials say the passenger 's name appeared on a manifest supplied by the airline , which was passed to U.S. authorities , who cleared the flight to depart . Were the proper security checks performed ? Yes , say Dutch authorities , who say he passed through normal procedures and that `` security was well-performed . '' He is known to have passed through a metal detector and his luggage was X-rayed . Extra attention is normally applied to passengers arriving from Nigeria because of concerns over fraud and smuggling . Nevertheless airports around the world have stepped up security procedures in the wake of the incident , increasing pat-downs and secondary searches . So how did the explosives get through ? Dutch authorities are at pains to point out that if the passenger had powders concealed upon his person or secreted bottles of liquid somewhere else , they certainly would not have been picked up by the metal detector . Is there any way of detecting these kind of explosives ? A preliminary FBI analysis indicates the device contained PETN , also known as Pentaerythritol Tetranitrate , a highly explosive chemical . Experts say this would have been picked up using a swab commonly used in secondary screening . A body scan , particularly the new 3D imaging scanners being trailed at some airports , would also have spotted something strapped to his body , even in the crotch area . Why were there no U.S. air marshal security officers on the flight ? U.S . Homeland Security Secretary Janet Napolitano told CNN federal air marshals are not posted on all flights . She said this was not due to budgetary constraints , but down to standard procedures , which see marshals posted randomly on certain routes . CNN 's Jeanne Meserve , Richard Quest and Barry Neild contributed to this report .
Dutch authorities say normal security procedures were carried out . Authorities say they would not have picked up secreted powders or liquid . Secondary checks should pick up similar devices .