Convicted penny-stock spammer Eddie Davidson walked away from a federal minimum-security prison camp in Colorado on Sunday, the U.S. Department of Justice said Tuesday.

Davidson, 35, had been serving 21 months in federal prison after pleading guilty to criminal spam charges in December. He is now considered an escapee and is being pursued by U.S. marshals, with help from the U.S. Federal Bureau of Investigation, the U.S. Internal Revenue Service and local police.

He earned millions of dollars between 2003 and 2006 by operating a spamming operation, called Power Promoters, out of his home. He would change the header information in his messages to make it appear as if they had come from legitimate companies such as AOL and then send them out to hundreds of thousands of addresses.

Davidson sent the messages on behalf of an unnamed Houston company, court filings state. He was asked to promote about 19 penny-stock companies, including one called Advanced Power Line Technologies in 2006 and 2007. He would earn fees based on the trading volume of the stocks he was promoting.

The business was lucrative: The Houston company paid Davidson about US$1.4 million for his services, court documents state.

Between 2003 and 2006, when his primary source of income was spam, bank account deposits into Davidson's account totalled about $3.5 million.

Davidson, of Bennett, Colorado, had been incarcerated at the Florence Federal Correctional Complex, about 45 miles south of Colorado Springs.