Known as 'vajralepa', the building materials date back to the Gupta era and were dug up by archaeologists in Bangladesh.

They find a mention in some Indian scriptures. They were excavated at Bhair Dhap site in Shibganj in Bogra district.

The Daily News quoted archaeologist Abdul Khalaque as saying that the material is like cement and made of banana, pulses and a broth prepared from boiling buffalo hide, starch and other inputs.

Antiques, including terracotta plaques with Brahmi inscriptions, were also found in a large quantity at the same site during the five month long excavation that started Nov 1.

The Brahmi inscriptions show ancient formation of some Bangla letters. The other relics found at the site include terracotta balls, ornamented terracotta, arch panels and ornamental bricks.