Rescue workers in Beirut dug through rubble and probed a collapsed building with sensors on Friday after signs of life were detected under a mound of debris one month after a huge explosion shattered the capital.

Workers pulled up chunks of concrete and masonry as they dug down in the residential district of Gemmayze after rescuers said on Thursday they had detected signs of a pulse and breathing, a Reuters witness said.

The Aug. 4 explosion at the nearby port was caused by massive amounts of badly stored ammonium nitrate. It killed about 190 people and injured 6,000, in a nation already crippled by economic crisis.

“The machine is saying that there is one alive, a heartbeat, and the dog is marking a dead body in a spot. This is the theory. Now we are searching to make sure,” said Mansour Al Asmar, a Lebanese volunteer rescue worker at the scene.

A crane helped lift steel girders and other heavy debris carefully from the ruins.

Residents gathered nearby, hoping someone could be found, while some said the government had not done enough to help.

“The government has been completely complacent, has been completely absent,” said Stephanie Bou Chedid, a volunteer from a group helping victims of the blast.

Near the site, Mohamed Khoury, 65, said he hoped someone was found alive but, even if only bodies were uncovered, “it’s important their families can find peace.”

The explosion ripped through a swathe of the capital, smashing up districts such as Gemmayze, home to many old, traditional buildings, some of which crumbled in the shockwave.

Rescuers, including volunteers from Chile, used scanning equipment to create 3D images of the wreckage to try to locate anyone alive, local television images showed.

The building being searched once housed a bar on its ground floor.

Lebanon’s army called for one minute’s silence at 6.07 p.m. (1507 GMT) on Friday to mark a month since the blast.