Just a quick point on the "oil slick/fuel" that has apparently been spotted - it should be easy to determine (certainly by taking a sample and analysing, and possibly just by looking) whether the fuel oil seen in the water is kerosene (and thus possibly from the aircraft) or comes from some other source (eg. a ship dumping tank residues).
There's a huge difference between jet A1 and oily ballast, and IMHO it wouldn't be difficult for someone who knew what they were doing to tell the two apart.
Final point on Jet A1 - it dissipates fairly quickly, so wouldn't necessarily be around/visible for long.