Gas company decided to shut off gas due to leak from backfeed
If it was two homes there are probably two meters. If you see a second meter turn one off .If they are tied together anywhere the one working meter will feed everything.  If however they removed the meter and piped straight across where the meter used to be.... you have an un metered line feeding the house. That's the first thing to look for. The place where the second meter used to be. EITHER WAY HAVE A PROFESSIONAL HAVE A LOOK