Section 62(1)(a) in The West Bengal Municipal Elections Act, 1994
(a)any ballot box used at a polling station or at a place fixed for the poll is unlawfully taken out of the custody of the Presiding Officer or the Municipal Returning Officer, or is accidentally or intentionally destroyed or lost, or is damaged or tampered with to such extent that the result of the poll at that polling station or place can not be ascertained, or(aa)[ any voting machine develops a mechanical failure during the course of giving, or recording of, votes; or] [Clause (aa) inserted by W.B. Act 9 of 2000, w.e.f. 21.2.2000.]