The Internet was extensively used for passing information to aid rescue and recovery efforts. For example, the official news agency Xinhua set up an online rescue request center in order to find the blind spots of disaster recovery. After knowing that rescue helicopters had trouble landing into the epicenter area in Wenchuan, a student proposed a landing spot online and it was chosen as the first touchdown place for the helicopters[not in citation given]. Volunteers also set up several websites to help store contact information for victims and evacuees. On May 31, a rescue helicopter carrying earthquake survivors and crew members crashed in fog and turbulence in Wenchuan county. No-one survived.
Try to answer this question if possible (otherwise reply "unanswerable"): On what date did a rescue helicopter crash with no survivors?
May 31