Give it a good clean all over with dry rags before using detergents at this stage. This may point to where the leak/leaks are coming from Has the oil level dropped significantly, if so if the leaks are not evident after cleaning start the engine after ensuring there is enough oil just to test for leaks. Also check the oil filter is secured in place.
Have you checked that the filter is tightly screwed in place? Just hand tight should do it. If it had vibrated loose it might explain the oil in that vicinity.