When federal officials descended on this small South Carolina town to investigate a kickback scheme that had caught up the mayor and another official, they stumbled across a web of corruption they believe is deeper and more widespread through the county.

Authorities began looking into the 8,000-person town more than a year ago, announcing in July 2008 that now former Union Mayor Bruce Morgan and former zoning administrator Jeffrey Lawson were charged with multiple federal crimes, including seeking bribes and plotting to take thousands in kickbacks from building contractors.