The investor, HCMC Management Authority for Urban Railways (MAUR), made the decision after failing to figure out why one of the Elastomeric Laminated Bearings pads had fallen out from its position between two beams on the line’s elevated section last October.

These pads are made from high purity elastomers that encapsulate layered internal steel reinforcing plates and are designed for use in bridge and building constructions for beam support.

The faulty pad was on the elevated section of the line, which runs 19.7 km (12.24 miles) from Ben Thanh Market in District 1 to Suoi Tien theme park in District 9.

The incident, which happened in October, was detected after cracks were seen on a section in Thu Duc District, now part of the newly established Thu Duc City.

Soon after, the contractor, a consortium comprising Vietnam’s Civil Engineering Construction Corporation No. 6 (Cienco 6) and Japan's Sumitomo Corporation, said they had fixed the issue, yet made no mention of how the pad had fallen and how it would affect the life and safety of the project.

The investor then decided to inspect the entire project, which was around 80 percent complete then.

For its part, the contractor said that the Covid-19 pandemic had not allowed it to bring foreign experts into Vietnam to carry out inspections. The contractor suggested having an independent consultant do the investigation.

While the MAUR has now agreed to this proposal, the identity of consultants has not been revealed.

It is known that the contractor has brought in two experts, one Japanese and the other South Korean, to HCMC; and that there is a French expert who is yet to arrive.

The investor had found last December that pads lighter than specified in approved designs have been used for supporting beams in the metro line. It said the EB1 and EB4 pads on the metro line’s elevated section weigh 117 kilos, which is nine kilos lighter than the design approved five years ago.

Both the pads were imported from South Korea, and around half of the pads used in the metro line No.1 are sourced there.

In January, the State Council for Pre-Acceptance Test of Construction Works concluded that the fault lay with the contractor. Since the project is still under construction and yet to be transferred back to the investor, the council decided that it will "respect all explanations of the contractor for the fault as well as its suggestions to handle the situation."

The metro route No.1 will have 14 stations – 11 on elevated sections and three underground.

Its construction is expected to cost VND43.7 trillion ($1.89 billion) in total.

It has been reported that work on the much-delayed project, which began in August 2012, is around 83 percent complete now.

The city had hoped to begin commercial operations by the end of this year, but the investor said in February that the service would be delayed yet again and can only commence next year.

HCMC plans to build eight metro lines running a total of 220 km.