Dolores and Bert Hitchens, FOB Murder
Available from used booksellers and (recently) as a part of the Library of America's Women crime Writers set, both in print and as ebooks.
I do not remember where I recently read about her books, but it reminded me that I had a read few of them a long time ago.
An older man (around 70?) dies after something happens in a railroad yard in LA. His daughter thinks he was murdered. A young Mexican is discovered in a freight car in a railroad car in LA. A young woman claims to have lost diamonds worth $60,000 from her luggage in Union Station in LA. Two railroad detectives, Collins and McKechnie, begin working these events separately (Collins has the death and the Mexican, McKechnie, the luggage. Because this is a mystery novel, they turn out to be related. The LA setting is almost incidental; I never got a real feel for that part of it. The plot, while good enough, is nothing special, and neither the dialoge nor the narrative rises above good. But it's a good enough procedural, and the narrative moves briskly to a satisfactory conclusion. The value of the diamonds, incidentally, would be about $530,000, adlusted to the current price level, which, for the people involved, would have been a tremendous fortune. Dolores Hitchens wrote 44 mystery novels between 1939 and 1973, 6 with her husband, Bert, whose day job was as a railroad detective. (https://en.wikipedia.org/wiki/Dolores_Hitchens) She was not a major figure in the genre, but her work was (in my experience; I've read 6 or 7 of her books from the late 1950s/early 1960s)) readable and reasonably reliable.