CHENNAI Electronic voting machines cannot not be tampered with, and the Pattali Makkal Katchi (PMK) was unable to demonstrate that this could be done when it was given a chance, said Chief Election Commissioner Navin Chawla here on Sunday.

Speaking to reporters at the Chennai airport, Mr. Chawla said that the PMK would be given one more chance to prove its claim.

The dates for the by-election to Tiruchendur Assembly constituency have not been finalised, he said in response to a question.