At least six people, including three Cambodian migrant workers, were killed late on Monday when a condominium construction project north of Bangkok collapsed, according to news reports, officials and witnesses at the scene.

Twenty-four people, at least one of whom is Cambodian, were also injured in the collapse, which was said to have happened while workers were pouring concrete on the top floor. Public health officials reported 33 people were buried in the rubble of the six-storey building – 24 Thais and nine foreigners.

A passerby told the Post by phone that shouts could be heard from people trapped under the debris as the search and rescue team attempted to find and extract survivors. Some victims were in critical condition, and a man whom health officials intended on rescuing by amputating his legs died yesterday morning while still trapped under a beam.

TV and internet footage showed people fleeing as the building crumbled in on itself, leaving only one shaft standing and still-moving workers caught between levels of the building.

The three Cambodians killed were working on the second storey when the structure collapsed; their bodies have not yet been located, according to the Ministry of Foreign Affairs. Those killed were among 30 Cambodian migrants at the site, all of whom were undocumented.

“Our ambassador visited a victim at the hospital, and we are also working with Thai police to demand the company pay compensation,” ministry spokesman Koy Kuong said.

Thai authorities yesterday announced on a government news service that they had mobilised drilling machines and backhoe tractors to rescue victims, and said the government would “expedite compensation for injured workers and the close relatives of the deceased”.

Kuong said the deceased Cambodians included Im Pheur, 27, from Prey Veng’s Mesang district; Yat Pheng, 19, from Prey Veng’s Svay Ontor district; and a third person identified only as Uch, 27, from Tbong Khmum’s Memot district. The injured Cambodian was Chhim Chan, 60, from Kandal’s Lvea Em district, he added.

“We are not sure whether to take the dead [when found] back home or not. We are waiting for contact from their families,” he said.

Kuong was unable to provide the name of the construction company responsible for the site, and Thailand’s Ministry of Foreign Affairs said that because yesterday was a public holiday, the relevant people could not be reached for comment.

The collapsed building in the Thanyaburi district of Prathum Thani province was to be one of two dormitories intended to provide housing for a nearby vocational college. The cause of the collapse is still under investigation but was determined to be in part due to a substandard construction process, according to the director of the Engineering Institute of Thailand, Suchatchavee Suwansawat.

Thailand has long come under pressure for a lack of safety precautions taken at construction sites, which typically employ foreign workers.

“Poor construction safety and standards result in frequent work accidents and fatalities in Thailand, and migrants are also particularly impacted,” Bangkok-based migration expert Andy Hall said.

In February, seven Cambodian workers were among 11 people killed at a Thai hospital undergoing repairs.

ADDITIONAL REPORTING BY BANGKOK POST