Rescuers say there are no signs of life in the rubble of a building they have been searching following a huge explosion in Beirut last month.

The search began on Thursday afternoon after a sniffer dog detected something in rubble in the Gemmayze area of the Lebanese capital.

Audio detection equipment had detected a pulse of 18 to 19 beats per minute, sparking hope there might be life.

However, on Friday morning, it was reported the signal had decreased to seven.

Rescuers had said it suggested someone could be alive or in a coma – or it could just be an object emitting a signal.

Around 50 rescue workers and volunteers, including a specialist team from Chile, continued to dig through the rubble for a third day on Saturday.

They said they would carry on despite there being a small chance of finding a survivor, and had narrowed their search.

More from World

Thermal imaging and scanning equipment was also being used as rescue teams removed debris, digging with their hands and shovels – careful to protect any survivors.

Blast site in Beirut
Image: Site of the blast in Beirut which killed some 190 people

“Always in search operations like this, you can neither lose hope nor absolutely say there is hope,” said George Abou Moussa, director of operations in Lebanon’s civil defence.

The huge blast on 4 August killed about 190 people, injured 6,000 more and devastated whole neighborhoods.

Chilean rescue team confirms they have found no signs of life in the rubble
Image: Chilean rescue team confirms they have found no signs of life in the rubble

Almost 3,000 tonnes of ammonium nitrate set off the explosion that tore through Beirut – considered one of the biggest non-nuclear explosions ever recorded.

Ceremonies were held on Friday to mark a month since the explosion tore into a city already reeling from a crippling economic crisis.

Paper lanterns in the shape of a Lebanese flag mark one month since the city's deadly explosion
Image: Paper lanterns in the shape of a Lebanese flag mark one month since the city’s deadly explosion

The ruined building where the search was continuing is located between the residential districts of Gemmayze and Mar Mikhael, which are among the hardest hit areas by the blast and home to many old buildings that crumbled as the shockwave ripped through.

The search was briefly halted on Thursday due to concerns about the unstable structure.

The area was inspected by the army following fears a wall might collapse and two cranes were bought so it could be safely removed.

A Syrian refugee family sit in the ruins of their building, destroyed by the explosion in Beirut
Beirut explosion: One month on

Days after the 4 August blast, more than 20 containers of ammonium nitrate were found at the port and moved to safe locations.

On Thursday, the army said it had found another 4.35 tonnes of the chemical compound in four containers near the port, which are being investigated.

A total of 25 people have being detained over the explosion, the majority either port or customs officials.