Rescuers are unlikely to find any more survivors of Mexico's earthquake still buried in the ruins, the emergency services chief said, with anger rising about a lack of information among relatives of an estimated 40 people still buried under rubble.

Tuesday marks one week since the 7.1 magnitude quake struck at lunchtime, killing 331 people, damaging 11,000 homes and leading to a outpouring of civilian volunteers to aid victims and grieving relatives.

Luis Felipe Puente, coordinator of Mexico's Civil Protection agency, told Reuters that rescuers would continue hand-picking through the debris at no more than four sites until Thursday.