PALU, Indonesia (Reuters) - In a tent next to the crumpled ruins of the Roa Roa hotel in Indonesia’s quake-hit city of Palu, relatives and friends of guests believed to be under the rubble await news as a desperate rescue effort goes on in the intense heat.

A rescue team member walks in front of the ruins of Roa-Roa Hotel after earthquake hit in Palu, Sulawesi Island, Indonesia, October 2, 2018. REUTERS/Beawiharta

Four days after a 7.5 magnitude quake and tsunami struck the coastal town on Sulawesi island, only three people have been pulled out alive from the ruined hotel, and nine bodies have been recovered.

About 50 people were believed to have been in the eight-storey building when the disaster struck.

A search and rescue team is using acoustic detectors to try to pick up any sounds from trapped survivors, as well as concrete and metal cutters, and saws.

“We’re using sound detectors that can pick up voices and knocking. All this takes time but it’s for safety reasons, for survivors and for our own team,” said rescue team head Agus Haryono.

An earth digger and crane arrived only on Monday because of difficult road access.

“We suspect there are still some survivors trapped inside. We are working with that in mind at the moment,” said Haryono, as he pored over blueprints of the building.

Among the group waiting for news, was Assegaf Umar, who was among a team of paragliders who had traveled to Palu to soar above its picturesque bay and steep green hillsides.

Umar, who escaped harm because he was staying at a different hotel, was clinging to hope that some of his fellow paragliders staying at the hotel might still be found alive.

“Even though by this time, after such an event, the body’s ability to endure is minimal ... we must remain optimistic,” Umar told Reuters.

The bodies of three of paragliders have been found, while another four, including a South Korean, were believed to missing beneath the rubble.

Rescuers on Tuesday retrieved the body of Ardi Kurniawan, who was well known among international paragliders.

Kurniawan had recently competed in the 2018 Asian Games held in Indonesia, and his team had won bronze medals at the 2017 and 2018 Paragliding World Accuracy Cup.

“We had gathered for a weekend festival and we were looking forward because this place is very beautiful and challenging. I am so sad that this happened,” said Umar.

The paragliders were in Palu for an annual festival in the capital of Central Sulawesi province, three days of arts, cultural events and sports.

One paraglider who lost his life, 20-year-old Gleen Mononutu, posted a photo on social media of himself soaring near cloud-topped hills on Sept. 28, the day the earthquake struck, along with a map of a flight path over Palu.

Another victim, Petra Mandagi, also posted a photograph of himself wearing an orange helmet and paragliding over Palu bay before disaster struck. It was unclear when the photo was taken.

“After bad weather and task stop yesterday, I can reach goal today,” he said in the caption accompanying the pictures on Instagram.

Mandagi’s friends and family replied in the comment section of the last photo, asking about his whereabouts after the disaster. Later, many posted condolence messages.

“RIP Petra, a skydive mate, a good friend,” said @ivykriyatavi.