Two Chinese workers were killed and eight others injured in Singapore Wednesday when scaffolding at a subway construction site collapsed, officials said.

It was the latest incident to hit Singapore's metro train network after two major breakdowns in December last year prompted a top-level investigation.

It was also the worst construction accident in Singapore since 2004 when a tunnel that was part of a subway line being built at that time caved in, killing four people.

Search crews on Wednesday found the two bodies submerged in wet cement and pinned down by planks of wood and metal from the collapsed scaffolding, a civil defence spokesman said.

Workers had been pouring concrete into a mould when the supporting structure gave way.

The first body was pulled out in the morning and the second was removed about five hours later. The Land Transport Authority said in an email to AFP that the fatalities were from China.

Nationals from China, India and Bangladesh form the bulk of workers in Singapore's construction sector.

During the search water was pumped to the affected area to keep the cement wet, as crews cut through metal poles and planks using acetylene torches to reach the bodies.

Eight other workers who suffered minor injuries were treated at a nearby hospital.

The civil defence spokesman said only the scaffolding collapsed and that the subway tunnel being constructed at the site "is still intact".

Officials described the accident as isolated, while the incident did not disrupt train operations and street traffic was also unaffected.

The tunnel is being built to link an existing underground train station with a new subway line under construction, and is slated to open in stages starting next year to meet the needs of a growing population.

It will add to the existing network operated by SMRT Corporation, which is 54 percent owned by state-linked investment firm Temasek Holdings.

Construction of other parts of the new line -- which will be operated by SBS Transit -- will continue and no major delay is expected, said Minister of State for Manpower Tan Chuan-Jin.

Singapore now has a population of over five million people and overcrowding in the metro system is a favourite gripe among residents.

A panel commissioned to investigate last year's train network breakdowns concluded that SMRT's metro system had been plagued by outdated equipment and poor maintenance for years.