The talk page actually mentions a kind of rebuttal to the organo-phosphate theory (which claims that the symptoms are not compatible with organo-phosphate poisoning):
http://ije.oxfordjournals.org/cgi/reprint/33/3/443
I can't really evaluate any of these claims since my expertise in this field is non-existant. Things might be as simple as described in the Guardian article (which portrays the organo-phosphate theory as self-evident but suppressed truth), or maybe more complicated. The forced resignation of all responsible researchers certainly smells very funny and the Spanish government seems to have tried to suppress the truth or at least give the impression that they were able to handle things by suppressing dissenting opinions.
[1] https://es.wikipedia.org/wiki/Enfermedad_del_aceite_tóxico_d...
[2] http://www.cbgnetwork.org/129.html
[3] http://cbgnetwork.org/1522.html
As early as 1981 relevant spanish newspapers were telling the same story:
[4] http://free-news.org/index02-pag.htm
[5] http://free-news.org/cambio01.htm
Edit:
This is the last interview to Dr. Muro: