A trick I use when I'm unsure of any obstructions behind a wall is to drill a very small hole that just makes it thru the wall surface. Then I take a coat hanger and bend one end so it has a slight arc. I then feed that end into the hole and twist the coat hanger around to see if it hits anything. You will easily be able to tell if there are any obstructions. I love this method because it will help inform you of any wiring and/or any plumbing or other obstruction prior to drilling.

EDIT: For additional safety, you can strip some electrical wire and take one of the stiff conductors (that still have insulation on it) and use that instead of a bare wire coat hanger.

A trick I use when I'm unsure of any obstructions behind a wall is to drill a very small pilot hole that just makes it thru the wall surface. Then I take some sturdy metal wire, insulated electrical conductor or a coat hanger and bend one end into an arc. Now feed that bent end into the hole and twist the coat hanger around to see if it hits anything. You will easily be able to tell if there are any obstructions. I love this method because it will help inform you of any wiring, plumbing, studs or other obstructions. I made a quick image to help explain it better.

A trick I use when I'm unsure of any obstructions behind a wall is to drill a very small hole that just makes it thru the wall surface. Then I take a coat hanger and bend one end so it has a slight arc. I then feed that end into the hole and twist the coat hanger around to see if it hits anything. You will easily be able to tell if there are any obstructions. I love this method because it will help inform you of any wiring and/or any plumbing or other obstruction prior to drilling.

A trick I use when I'm unsure of any obstructions behind a wall is to drill a very small hole that just makes it thru the wall surface. Then I take a coat hanger and bend one end so it has a slight arc. I then feed that end into the hole and twist the coat hanger around to see if it hits anything. You will easily be able to tell if there are any obstructions. I love this method because it will help inform you of any wiring and/or any plumbing or other obstruction prior to drilling.

EDIT: For additional safety, you can strip some electrical wire and take one of the stiff conductors (that still have insulation on it) and use that instead of a bare wire coat hanger.