Seven San Francisco mayoral candidates sent a letter on Sunday urging the U.S. Department of Justice and California's Secretary of State to send federal observers and state election monitors immediately to watch over the city's mayoral election, which is now underway.

Jeff Adachi, Dennis Herrera, Michela Alioto-Pier, Joanna Rees, Leland Yee, John Avalos, and David Chiu signed the letter.

It came less than 48 hours after The Bay Citizen and the San Francisco Chronicle published eyewitness accounts of possible voter fraud by workers for the SF Neighbor Alliance for Ed Lee for Mayor 2011.

According to those accounts, workers for the independent political organization helped a group of mostly elderly Chinese voters fill out their absentee ballots.

In some cases, the workers overlaid stencils — thin, transparent plastic panels with horizontal slits to help draw straight lines — on top of the ballots to guide the voters to where they should mark their ballots.

On Friday, Bay Citizen journalists witnessed a worker, who identified herself only as Wong, help an elderly voter fill out his ballot and then place what appeared to be an envelope containing the ballot in an orange bag. She removed the envelope from the bag and put it back on a table after a Bay Citizen photographer began taking pictures of the incident.

In their letter, the mayoral candidates wrote that such "electioneering activities" targeting Cantonese-speaking voters may "impinge on their their federally protected voting rights and also violate provisions of the California Elections Code and other state laws."

The candidates addressed the letter to Debra Bowen, California's Secretary of State, and Thomas E. Perez, the Assistant U.S. Attorney General for the Voting Rights Section of the Department of Justice's Civil Rights Division.

The letter states that by "completing ballots for voters," by using stencils "to prevent voters from marking their ballots for other mayoral candidates," by "taking ballots into their possession," workers for the Alliance may have violated the U.S. Voting Rights Act of 1965, among other laws. Under state elections code sec. 3017, only a spouse or close relative can return a completed ballot for a voter.

When questioned by The Bay Citizen, workers for the Alliance denied any wrongdoing.

John Arntz, the head of the San Francisco Elections Department, referred the case on Friday to District Attorney George Gascon for further investigation. Although Election Day is Nov. 8, voters can cast ballots now.

In response to the letter, Tony Winnicker, a spokesman for Lee's campaign, said on Sunday evening that the mayor “fully supports an investigation by whatever appropriate authorities” of the SF Neighbor Alliance.

“We should all be united around protecting the integrity of this election and the right to vote,” Winnicker said. “In the past the Chinese community had been disenfranchised for too long for that right to now be undermined by improper activities, whether it’s ballot handling or coercion.”

Enrique Pearce, who heads the Alliance, could not be reached for comment. Pearce also headed the "Run, Ed, Run" campaign to draft interim Mayor Ed Lee to run for a full term.

This summer, Lee’s political opponents repeatedly accused the "Run Ed Run" campaign of ethical improprieties.

On Sunday morning, Lee angrily denounced the Alliance during an appearance on the CBS 5 Early Edition newscast.

“They have nothing to do with my campaign,” Lee said. “I think it’s moronic for them to be doing things that would interfere with people or individual’s right to vote, and if they compromise anyone, they’re not doing me any good at all.”

At one point, Lee sounded exasperated.

“I don’t want them to do this; I’ve told them to stop through our campaign,” Lee said. “If they’re not going to stop, they have to be compliant with the law, and they should be held accountable.”