Managing director Mr Atanas Maina said the suspension of work followed concerns raised by the project's supervisory consultant over the design of the line's culverts. He said the suspension allowed for a harmonisation of standards and has now resumed after main contractor China Roads and Bridge Corporation (CRBC) "adhered to the set requirements and submitted the requisite information and documents."

"The supervisory consultant has to ensure high-quality construction with full compliance to best international practices in engineering design, working drawings and technical specifications, monitor and approve the pre-construction activities," Maina says. "The design that the Chinese are using is not what Kenyan engineers have used before and this was the main bone of contention in this project."

However, Maina insisted that "all other works from earthworks, sleeper and bridge T-beam pre-casting works, bridges and piling works were still going on in earnest," while the suspension was in force over the past few days.

This is the second time since February that the issue of standards of the materials and design used for the $US 3.6bn railway project has emerged.

In February CRBC had raised concern over the quality of cement and steel produced and supplied by Kenyan sub contractors, a claim dismissed by the Kenya Association of Manufacturers, which said that CRBC was hoping to import the materials from China.

Work was also suspended on the project in October 2014 following a dispute over compensation with landowners, delaying the start of construction until December. The project is expected to take 3.5 years to complete.