Adventures of Superman #499 (1993)

Lex Luthor II and Supergirl are awakened in the middle of the night by an alarm Luthor had installed in Superman's tomb. With the surveillance cameras disabled, infrared sensors are show movement leaving the tomb. Thinking that Superman's alive, Lex sends Supergirl to investigate via a secret tunnel he installed. However when she goes to investigate, an undercover cop sees her enter the tomb who calls Dan Turpin. Supergirl sees the coffin missing and a hole drilled into the tomb's walls. Outside the tomb, Jose Delgado, despite being dumped by Cat Grant, considers becoming Gangbuster again, even though he's given a passive warning from Inspector Henderson not to. Lois, Jonathan, and Martha spend their night comforting one another, before Jonathan and Martha return to Smallville the next day. Supergirl, via radio contact, tells Lex that the hole in the wall was made from the outside and that the tunnel is sophisticatedly made. Turpin arrives on the scene and enters the tunnel as well. Meanwhile in Suicide Slum, Gangbuster and Bibbo take care of some low-lifes. Back in the tunnel, Supergirl hears voices coming from a fork in the tunnel path, suddenly she comes into contact with the Underworlders. Turpin catches up to her and helps her fend them off. After a couple of live grenades are set off, Supergirl and Turpin hightail it out of there, narrowly escaping the explosion and debris cave-in. Supergirl returns to tell Lex everything, while Turpin and Maggie Sawyer have a good hunch that Cadmus has Superman's body.