Questions have risen following the discovery of a mysterious concrete at Nairobi's City market. 

The discovery was made by Nairobi Metropolitan workers who were doing renovation works at the market. 

The discovery is likely to spark archaeologists and architectural historians' interest in what could be beneath the crucifix-like concrete.

Following the discovery, archaeologists from the National Museums of Kenya were summoned to inspect the site as the renovation works were halted.

The museum's team dug around the cross-slab, which has some pipe points on it as workers wondered whether they had stumbled on a cemetery.

"What we found is that it is made of solid granite, and beneath it, there is another heavy concrete layer reinforced with heavy metal. We don't know for sure whether it was an ablution block or its historical significance," said Dr. Emmanuel Ndiema, the archaeologist who assessed the site.

"While it has no inscriptions on it, the cross was left intact by the museum's team – hoping to in future to x-ray underneath the slab. We shall use ground penetration radar or portable CT scan to check the site," he added. 

City Market was built in the 1930s as a European-only market to replace the Jeevanjee market, which had been brought down due to unsanitary conditions.