A nursing home management group that locked out 100 workers from a facility Tuesday says unionized employees are picketing illegally. As a result, it is threatening to lock out 700 more.

Officials from HealthBridge Management said it blocked union members out its Milford, CT, facility due to frustration stemming from 10 months of contract negotiations with the Service Employees International Union, The Hartford Courant reported. Lisa Crutchfield, HealthBridge’s senior vice president of labor relations, told the newspaper that picketing workers did not give the company the required 10-days notice of their strike.

The SEIU’s attorney, however, claims HealthBridge controlled the timing of the disruption, rendering the 10-day notice policy moot. The union is accusing HealthBridge management of using “hardball tactics” by planning lockouts during the holiday season.

HealthBridge said in a statement that it has ruled out lockouts at its five other facilities, but officials also said they could change their minds if workers continue to picket at the Milford facility. Nurses and therapists are not affected by the strike, but replacement staff have been hired for nursing aides, dietary and laundry workers, and housekeepers.