A crane overturned at a Metro construction site in south Delhi on Saturday afternoon, but no one was injured in the incident which comes three weeks after a metro train derailed in New Delhi.

Putting the blame on "deficiency" in design and material for the July 12 mishap which claimed six lives, Delhi Metro on Tuesday claimed that a design consultant firm which inspected the site "misled" them and the contractor about the condition of the pier which collapsed.

The Delhi Metro Rail Corporation has blacklisted several of its contractors, including Gammon India, over the accident in Delhi which claimed six lives.

Eighteen piers on three corridors of the Delhi Metro have developed "minor" cracks and the DMRC has kept them under the observation of its engineers as it does not want to take any chances after the July 12 mishap that killed six persons.

Cracks have been noticed on two piers with cantilevers on the newly constructed Yamuna Bank- Noida Metro line during an inspection of all Metro structures, a move taken up after the July 12 mishap which claimed six lives.