Each of the elastomeric laminated bearings pads has moved from its position between two beams by 7-11 millimeters, the HCMC Management Authority for Urban Railways (MAUR) reported Friday following an inspection.

They are in the elevated section of the line and near the depot in Thu Duc City.

Two each were imported from South Korea and Japan.

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

In January a similar error was detected in the elevated section after a pad fell off its position and another had moved out of position, leading to cracks in the beams. Both were imported from South Korea, as are around half of all pads.

Now with four more faulty pads, MAUR has concluded that this error is "systemic."

It has ordered the contractors, a consortium comprising Vietnam’s Civil Engineering Construction Corporation No. 6 (Cienco 6) and Japan's Sumitomo Corporation, who said they had fixed the issue, to swiftly clarify the status and figure out the reason for the recurring problem.

The line is still under construction and no part of it has been handed over to the city.

Last month MAUR decided that an independent consultant should investigate why the supporting pad fell from its position after it failed to find out the cause.

The State Council for Pre-Acceptance Test of Construction Works had in January concluded that the fault lay with the contractor.

The 19.7-km (12.24 miles) line from Ben Thanh Market in District 1 to Suoi Tien theme park in District 9 will have 14 stations, 11 above ground and three under it.

It is expected to cost VND43.7 trillion ($1.89 billion).

Work on the much-delayed project, which began in 2012, is 83 percent complete.

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.