The official death toll after Mexico's 8.1 magnitude earthquake has risen to 96 as more deaths were confirmed in the hard-hit southern states of Oaxaca and Chiapas.

An explosion has ripped through Mexico's best-known fireworks market on the northern outskirts of the capital, killing at least nine people, injuring scores more and sending a huge plume of smoke billowing into the sky.

Photographs of a blindfolded man circulating on the internet appear to show a former Mexican presidential candidate missing since last weekend and feared kidnapped.