Kafka source connect poll method called by multipl

Question

I have written a file source connect, I tried starting it in standalone and as well as distributed mode.. I notice sometimes the poll method is called by multiple threads. I understand if we create a task - that will be assigned to a worker which assigns a single thread and poll method is called by only this thread. But in my case it is behaving differently. Can somebody please explain me under what circumstances a source task is executed by multiple threads concurrently. This is creating issue for my implementation

Thanks in advance.