The European Food Safety Authority (EFSA) and 6 EU member states have carried out independent assessments of the controversial paper by Séralinia et al. published on the 19th September 2012 in the Journal Food and Chemical Toxicology that concluded that a strain of GM maize and a pesticide could increase incidence of cancer in rats.
The general consensus was that the conclusions of the paper were not supported by the data presented. The EFSA had also requested further documents regarding the study from Séralinia et al. but had had no response before this assessment was completed. The open letter written by the group to defend their publication did not answer all of the questions asked.
The final review of the publication is available from the EFSA website