。
She said she had seen such-and-such people there.
Literal
She [topic-は] there [at-で] such-and-such [genitive-の] people [object-を] saw [quotative-と] said.
しかじか ('such and such, so-and-so') is a placeholder phrase used when the actual content is being elided in retelling — the speaker is deliberately abstracting away the specifics. It's the verbal equivalent of writing '...' or 'blah blah' — common in legal or formal-style summaries (かくかくしかじか 'as I just described'). The genitive の lets it modify 人々. The と marks the embedded clause as the reported content of 言う; combined with the past 言った, the structure is the workhorse Japanese reported-speech frame.