BAD AXE, Mich. (AP) — A couple who own a dairy farm in Michigan's Thumb region pleaded guilty Tuesday to hiring illegal immigrants and agreed to pay a $2.7 million penalty.

Johannes and Anthonia Verhaar acknowledged they had employed about 80 illegal immigrants from 2000 through much of 2007. The government said the Verhaars ignored warnings that some employees were not authorized to work in the U.S. They made the plea in U.S. District Court in Bay City.

"Criminal charges and fines are among the government's most effective tools to ensure employers maintain a legal work force," Brian Moskowitz, head of Michigan investigations at Immigration and Customs Enforcement, said in a prepared statement.

"An important component of immigration enforcement is prosecuting those who employ undocumented workers," said U.S. Attorney Barbara McQuade.

The farm, called Aquila Farms, also entered a guilty plea. Messages seeking comment were left with Verhaars' attorneys.

An article in The Bay City Times says the farm has about 2,500 head of cattle.

The couple face up to six months in prison when they're sentenced on Oct. 5. The farm is in Huron County's Colfax Township. It's just west of Bad Axe and about 110 miles north of Detroit.

Copyright 2011 The Associated Press.