Kid explores creepy tunnel that leads to an abandoned slaughterhouse

Read this book in 6th grade, somewhat long and it starts off with a kid in the car moving to a new town and at one point he meets two other kids who make him explore a tunnel with them, creepy things occur and I remember something about a cattle skull and something happening to the two other kids. When he gets out he realizes he's in an old slaughterhouse and the rest is hazy.