Argentine rescue workers were on Tuesday scrambling to reach several people trapped under the rubble of a ten-story hotel building that collapsed in the seaside resort of Villa Gesell.
At least one person died when the Dubrovnik hotel, an apartment hotel that was undergoing unauthorized renovations, collapsed in the middle of the night.
Up to nine others were still missing, rescue officials said.
Some of the missing people had been working on the site, local officials said.
"The hotel imploded, it fell on itself and the last three floors tilted and crushed 25 percent of the building that was next door," Javier Alonso, the security minister for Buenos Aires province, where Villa Gesell is situated, said.
He said neighbors heard something "like a creaking and a vibration in the floor and a few minutes later it collapsed."
He warned that the rescue process would be "slow" given the amount of debris but stressed that survivors were sometimes found under rubble up to a week after such collapses.
The body of a man in his eighties was found in the debris.
Between seven and nine people were believed to still be trapped, said the head of the fire service operation, Hugo Piriz.
"It was like a missile fell and split the building in two," a neighbor told the TN television channel.
A 79-year-old woman from the building next door was rescued alive with injuries after she was heard knocking on a pipe.
"We got closer to the noise and managed to hear the voice. It was hard work, it took several hours," Piriz told reporters.
More than 300 rescuers, using drones, sniffer dogs and probes with cameras and microphones, were searching for other survivors.
The hotel was built in 1986.
Villa Gesell municipality said that work was being carried out at the facility "clandestinely, without complying with municipal regulations" and that it had already been halted by the authorities in August.
The foreman and three bricklayers were detained for questioning.
Relatives of the victims gathered near the building to await news of their loved ones as a bulldozer removed debris.
"Time is going by and I want my son alive. I want my son alive and I want him whole," Silvana Perhauc, the mother of one of the missing people, said.