SAN FRANCISCO (CBS/AP) – Candidates vying for the San Francisco’s mayor’s seat are requesting federal and state monitors for the Nov. 8 election after allegations of ballot tampering in early voting.

The seven candidates are basing their concerns on local media reports claiming that members of a neighborhood alliance supporting incumbent Mayor Ed Lee have been helping Cantonese-speaking residents fill out ballots.

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The candidates outlined their concerns in a letter to the U.S. Department of Justice and California secretary of state on Sunday. They want an investigation into reports that the alliance used stencils that prevent voters from marking their ballots for candidates other than Lee.

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The candidates include City Attorney Dennis Herrera, Board of Supervisors’ President David Chiu and Public Defender Jeff Adachi.

Lee has said his campaign is not affiliated with the alliance.

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