Hanging something on wall shared with old washer/dryer unit

I got one nail in for my shelf above the my range and the second seems to be hitting something too hard to pass though. I'm wondering if it's a bad idea to drill here because the washer and dryer share the wall behind the oven/range? Is it likely I'm hitting the vent or something?

Much of my house needs screws instead of nails due to plaster but in the past the interior kitchen walls have always held nails up til now.