SEATTLE — U.S. Immigration and Customs Enforcement reached its highest number yet of companies audited for illegal immigrants on their payrolls this past fiscal year.

Audits of employer I-9 forms increased from 250 in fiscal year 2007 to more than 3,000 in 2012. From fiscal years 2009 to 2012, the total amount of fines grew to nearly $13 million from $1 million. The number of company managers arrested has increased to 238, according to data provided by ICE.

The investigations of companies have been one of the pillars of President Barack Obama’s immigration policy. When Obama recently spoke about addressing immigration reform in his second term, he said any measure should contain penalties for companies that purposely hire illegal immigrants. It’s a stand he likely will highlight as his administration launches efforts to revamp the nation’s immigration system.

“Our goal is compliance and deterrence,” said Brad Bench, special agent in charge at ICE’s Seattle office. “The majority of the companies we do audits on end up with no fines at all, but again it’s part of the deterrence method. If companies know we’re out there, looking across the board, they’re more likely to bring themselves into compliance.”

While the administration has used those numbers to bolster their record on immigration enforcement, advocates say the audits have pushed workers further underground by causing mass layoffs and disrupted business practices.

When the ICE audit letter arrived at Belco Forest Products, management wasn’t entirely surprised. Two nearby businesses in Shelton, a small timber town on a bay off Washington state’s Puget Sound, had already been investigated.

But the 2010 inquiry became a months-long process that cost the timber company experienced workers and money. It was fined $17,700 for technicalities on their record keeping.

“What I don’t like is the roll of the dice,” said Belco’s chief financial officer Tom Behrens. “Why do some companies get audited and some don’t? Either everyone gets audited or nobody does. Level the playing field.”

Belco was one of 339 companies fined in fiscal year 2011 and one of thousands audited that year. The audits, part of a $138 million work site enforcement effort, rely on ICE officers scouring over payroll records to find names that don’t match Social Security numbers and other identification databases.