Claims that vote-rigging helped the Conservatives win control of Coventry City Council for the first time in almost 30 years are being investigated by West Midlands Police.
Inquiries are centred on Foleshill, an Asian-dominated ward in the north of the city, which Tory candidate Altaf Adalat took from Labour with a majority of just six votes on May 4.
An election petition lodged by defeated Labour candidate Malkiat Singh Auluck alleges that the identities of ten voters were stolen in order to give the Conservatives an unfair advantage.
None of the ten people concerned was in the country at the time of the election, but all apparently voted according to registers kept by polling station clerks.
Three are said to have voted by post from an address where they do not live.
There is no suggestion that Coun Adalat did anything wrong or had any knowledge of the alleged malpractice.
A preliminary hearing of the allegations in the High Court could be up to three months away, given the volume of vote-rigging claims from across the country. More than 300 petitions have been lodged.
The court could confirm Coun Adalat's victory, order a re-run of the Foleshill election, or award the seat to Labour.
The Conservative victory in Foleshill helped the party to a slender majority on the council for the first time since 1977.
David Cameron, the Conservative Party leader, visited Coventry on the day after the result was announced to declare that the party was now capable of winning in the industrial heartlands.
Coun Adalat's victory was one of only two Tory gains on May 4, but it was enough to strengthen the party's grip on power.
Chris Hinde, the Coventry returning officer, had already called in police during the campaign after discovering 70 suspicious-looking applications for postal votes in Foleshill.
John Mutton, leader of the Labour opposition group, said previous attempts to expose "irregularities" in Foleshill had failed because people were frightened to come forward.
Coun Mutton (Lab Binley & Willenhall) added: "We have been able to identify ten people who were not in the country when the election took place yet they were down as having voted. We have statements from some of them and have passed the information on to the police. We will continue to seek further evidence of malpractice."
Labour is also looking at claims that several people who had died before May 4 were shown on the register as having voted. "They were resurrected. it's a miracle," Coun Mutton added.
Coun Mutton said Labour would be asking for a re-run of the election in Foleshill.
Ken Taylor, the leader of Coventry City Council, described the petition as a "high-risk strategy".
Coun Taylor ( Con Earlsdon) added: "If it goes to a re-run I have no doubt that we shall win it again."
A West Midlands Police spokesman said: "We are conducting inquiries in connection with an election petition in the Foleshill area of Coventry."