A Chilean search and rescue team working in the rubble of Beirut say they've detected a possible heartbeat of someone trapped under a building which was destroyed in the August 4 explosion.
If true, it means the survivor has been stuck under the wreckage for 29 days.
A sniffer dog was reportedly the one who alerted rescuers to the presence of a potential survivor. A major search operation is now underway.
Crowds of people have gathered to watch the rescuers as they dig through the rubble in an attempt to locate the source of the heartbeat.
BBC journalist Claire Read tweeted: "Whispers of 'Is it true? Could someone be alive??' One month tomorrow since Beirut blast. The crowd is buzzing and the rescuers hush us as they listen and search."
Photos from the scene show members of the military standing with workers in high-vis jackets as they inspect the wreckage. Members of the public, most wearing face masks, can be seen filming on their phones.
"The wait for news as rescue team search for survivors," reporter Orla Guerin tweeted.
"A young woman from the fire department that has just been dropped down through the rubble to hole below. Nothing is certain but some local people are daring to hope."
The rescue team arrived in Lebanon three days ago to help sort through the wreckage. The same team reportedly rescued a man in Haiti 27 days after he was trapped by an earthquake.
They have said it could take until midnight local time for there to be any news on whether someone really did survive the explosion.
It's currently evening in Beirut and the light is fading, so rescuers have brought in flood lights to illuminate the area of the search.
The port of Beirut, the capital of Lebanon, was obliterated on August 4 after two huge blasts from a warehouse where ammonium nitrate was being stored.
At least 190 people were killed and 300,000 more were made homeless by the disaster, which prompted the Lebanese government to resign days later.
Politicians were accused of negligence and corruption that saw 2,750 tonnes of ammonium nitrate stored for six years without safety measures at Beirut's port.