Rescuers in Beirut said they detected a possible heartbeat under the rubble of a building destroyed by the blast on August 4.

A sniffer dog reportedly alerted rescuers to the presence of a potential survivor, sparking a major search.

If someone was found alive, it would mean that the person has been stuck under the wreckage for 29 days.

Specialist sensor equipment has been brought to the Mar Mikhael area following unconfirmed reports that a heartbeat was detected.

"These (signs of breathing and pulse) along with the temperature sensor means there is a possibility of life," rescue worker Eddy Bitar told reporters at the scene.