Police are studying 190 incidents of suspected bogus electoral registration in Bordesley Green - one of the wards at the centre of Birmingham's 2004 postal vote scandal.
Specialist investigators analysing trends of registration to vote by post in today's city council elections said there were grounds to suspect fraudulent activity.
The police statement followed the arrest last week of Mohammed Khan, the Liberal Democrat candidate for Nechells, on suspicion of committing postal vote fraud.
Mr Khan, who lives in Bordesley Green, was questioned by police along with his wife, Naseem Akhtar, who was arrested on suspicion of conspiracy to defraud the electoral process.
Both were granted police bail until June and have denied any wrongdoing.
Bordesley Green and Nechells are at the heart of an intense battle for votes between Labour and the Liberal Democrats, with both parties fighting to win in the Asian-dominated inner city wards.
Five separate police inquiries into suspected postal vote fraud in Birmingham are taking place.
However, despite intense police activity in recent weeks, no one has yet been charged with an offence.
The police were unable to bring prosecutions in 2004, when an election court uncovered widespread ballot-rigging and fraud by Labour councillors and supporters in Bordesley Green and Aston.
A high court judge likened Birmingham to a banana republic, prompting the police and council to redouble their efforts to tackle fraud.
West Midlands assistant chief constable Stuart Hyde confirmed last night that he would respond to a request from Mike Whitby, the leader of Birmingham City Council, for special patrols to guard polling stations.
Mr Hyde said the necessity for a police presence would be determined on a case by case basis.
He said the police would continue to work closely with the council to identify ballot riggers. Anyone trying to vote in a false name would be committing a criminal offence and dealt with accordingly.
Mr Hyde added: "This is evidence of the close working relationship between ourselves, our partner agencies and the electoral registration office.
"Everything reasonably possible will be done to bring to justice those who commit election fraud."
The number of postal vote applications in Birmingham stands at 58,000, down from the record 70,000 in 2004.
However, there have been increases of up to 30 per cent in five wards.