BOSTON (CBS/AP) — Thousands of Janitors in Boston may walk off the job after their union voted to authorize a strike.

The Service Employees International Union voted to allow negotiators to declare a strike if a deal can not be reached with employers by the end of the month.

Janitors complain that employers offer them between three and 20 hours a week, a move that prevents them from qualifying as fulltime workers and deny them access to insurance provided by employers.

WBZ NewsRadio 1030′s Kim Tunnicliffe Reports

About 1,400 janitors represented by Local 615 of the Service Employees International Union voted Saturday by a standing vote to authorize a strike. The union cited reports of workers being met with illegal threats and intimidation.

The Local 615 of the SEIU represents 18,000 property service workers — including 14,000 janitors — in Massachusetts, New Hampshire and Rhode Island. The union says more fulltime jobs creates stronger economies.

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