Election officials offered city workers masks and gloves to ward off any biological agents that may be packed into mail-in ballots arriving at the election commission between now and Nov. 6.

"The chances of anything happening are pretty slim, but we still need to take precautions," said Carrie Kellogg, logistics director for the Denver Election Commission.

The election for school board members and bond proposals is the first all mail-in election for the city.  The decision to hold the election through the mail was made months before anthrax-tainted mail started infesting media and government offices on the East Coast.

"I don't think it's a problem," election judge Janet Mills said. "If we were in New York and Washington, I might be worried."

Election judges began opening the first returned ballots Monday.

The Associated Press contributed to this report.