Rescuers search for survivors after thermal scans show signs of breathing and heartbeats beneath debris.

Rescuers have pulled two people from the rubble of a collapsed building under construction in the Philippines, bringing the death toll to three, officials have said, as crews continue search and rescue operations at the site.

One of the two victims had a pulse when he was retrieved, but later died, while another suffered cardiac arrest while still trapped, Maria Leah Sajili, an information officer at Bureau of Fire Protection, said in a phone interview with the Reuters news agency on Monday.

Officials said an investigation is under way into what caused the collapse of the multistorey building in the city of Angeles, north of the capital, Manila.

Rescuers were also working to retrieve another body buried under the debris, Sajili said, but it would only be added to the official toll once it has been recovered.

Sajili said there could be more victims trapped, after thermal scans detected signs of breathing and heartbeats beneath the rubble.

The number of missing stood at 17, most of them construction workers listed as being on duty at the site, Sajili said.

Officials said up to 70 people were employed at the construction site, though most had gone home for the weekend.

Alfredo Albis, 55, told the AFP news agency he was asleep at a barracks for workers about 5 metres (16 feet) from the structure when it gave way.

“I have two cousins who are still trapped there. They were working here to earn for their families and [they] are missing,” he said, adding that “there’s a possibility that my relatives are dead”.

Sajili, the fire bureau spokeswoman, said that “rescue in [a] building collapse is very challenging, since any sudden shift triggered by the movements of our rescuers can cause areas to move and people under can get crushed”.

Sudden movements “may also bury our responders”, she said, explaining why this phase of the operation had to be done mostly manually.

If no more survivors are found, mechanical diggers and other heavy equipment will be brought in to clear debris and recover bodies, she said, but gave no timeline.

The cause of the collapse is not known.

Angeles City Mayor Carmelo Lazatin told reporters that authorities were trying to locate the building owner to get answers, including clarity on the number of workers at the site.

Families have grown increasingly impatient and frustrated with the pace of the search and rescue operations.

Lea Casilao, who travelled from Manila, said she only wants regular updates about the status of her husband, a construction worker believed to be trapped beneath the rubble.

“My youngest child keeps asking, but I do not have answers,” the 47-year-old said.