Rescuers in Beirut resumed a search through the rubble of a collapsed building early Friday in a deadly explosion that rocked the capital a month before ago after a pulsing signal discovered Thursday raised hopes that someone could be alive underneath the destruction.

A sniffer dog with a Chilean search-and-rescue team first detected something on the Gemmayzeh Street -- one of the hardest hit in the Aug. 4 blast -- as the team swept that part of the city. Then using audio detection equipment, the team found what could be a very slow heartbeat – about 19 beats a minute.

The search was briefly suspended for the night Thursday night before starting up again Friday but some volunteers worked through the night.

Rescue workers used cranes, a bulldozer and their bare hands in the dangerous and delicate rescue effort.

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At least 191 people were killed and more than 6,000 injured when nearly 3,000 tons of ammonium nitrate ignited at the port in early August.

Rescuers acknowledged it’s unlikely someone could survive underneath a demolished building for a month but refused to be deterred from the effort.

“Ninety-nine percent there isn’t anything, but even if there is less than 1% hope, we should keep on looking,” said Youssef Malah, a civil defense worker. He said his men would continue working throughout the night Thursday, adding that the work was extremely sensitive.

Francesco Lermonda, a Chilean volunteer, however, said the equipment detected the sign of a human and it’s not impossible for people to survive for 30 days under those conditions.

After hours of searching the work briefly stopped after sunset Thursday before some protesters arrived at the scene claiming the Lebanese army had asked the Chilean team to stop the search. The protesters started searching themselves until members of Lebanon’s Civil Defense team arrived an hour after midnight and resumed work.

The army issued a statement Friday saying the Chilean team stopped work half an hour before midnight for fears that a wall might collapse, endangering them. It added that army experts inspected the site and two cranes were brought in to remove the wall and the search resumed.

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On Friday morning, rescue workers were slowly removing debris with their hands and shovels, digging a hole in the building debris. The more they dug, the more careful the work became to protect any possible survivors under the rubble. Later, they brought a 360-degree camera placed at the end of a long stick and pushed it into a hole in the building.

The Associated Press contributed to this report.