OAK BROOK, Ill. (CBS) – A day after they rallied in Chicago’s Loop, union janitors took their strike threat to the suburbs, where they staged a large and noisy demonstration for their cause.

They marched and stopped traffic along the busy intersection of Route 83 and 22nd street in Oak Brook, chanting and speaking in English, Spanish and Polish. The janitors, who work in buildings and schools in the city and many suburban office buildings, have a contract that expires this Easter Sunday.

Laura Garza, Vice President of Service Employees Union Local 1, says they are fighting an old battle. The union went on strike 12 years ago, she says, and rallied at the same suburban intersection.

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The workers have authorized a strike this time, too; but SEIU officials say they hope it does not come to that. Wages and health insurance are the major issues.

If a strike goes ahead, some of the buildings and offices that would be affected by a strike include Bank of America, JP Morgan Chase, General Electric, CME Group, Boeing, AT&T, Kraft, United Airlines, and Tishman Speyer.

The janitors voted to authorize the strike over the past weekend. They also rallied at Teamster City at the intersection of Ashland Avenue and Jackson Boulevard on Saturday.

SEIU cites the Economic Policy Institute’s calculation that the cost of living for a family of four in the Chicago area is $51,319 a year — $20,000 more than the average janitor makes.

The contract covers:
• 4,000 janitors in downtown commercial office buildings
• 3,000 in suburban commercial office buildings
• 2,700 in public schools and city of Chicago facilities
• 3,500 in malls, universities and other buildings.

Bargaining resumed Thursday and is expected to continue through the weekend.