There are two boys in a compartment of a train carriage. There are some other children playing outside in the corridor of the train. (Morphling: I am translating 通路 as "corridor". I assume that is what it means in the context.) In the first part of the sentence, I think the girl is talking about the other children playing in the corridor, not the two boys in the compartment. The girl has come from another part of the train. In terms of the meaning of the story, it is plausible that 見に来てみた refers to her coming from another part of the train to see what the commotion in the corridor is about, or her coming into the compartment from the corridor to see what the boys are doing.
When I read the Japanese version I thought it referred to the former. However, on checking the English, it seems it should mean the latter. I wondered whether I had understood the Japanese incorrectly (and if so, why) or whether the Japanese was ambiguous.