Exam SHRM-SCP topic 1 question 5 discussion

In one of the warehouses of a retail company, several international employees complain to HR that the warehouse manager has forbidden them from speaking in their native language in the workplace. The HR manager speaks with the warehouse manager, who says there have been several reports that the international employees only interact with each other and they have difficulty conversing with the local employees due to language barriers. The HR manager also learns that the international employees can speak the primary language used in the company well enough to understand instructions from their supervisors. Fortunately, there have been no incidents of safety issues where language has been a barrier between local and international employees. However, senior management believes there is a lack of rapport between local and international employees and instructs the HR manager to resolve the issue.
The international employees tell the HR manager that the warehouse manager threatened to discipline them for speaking their native language at the workplace. Which action should the HR manager take to best foster a supportive workplace?