Multiple Auctions for same property?

Yesterday I searched the site for properties that were supposed to be on auction today.? I limited my search to the S.F peninsula and with homes (etc) that had starting bids significanlty less than the estimated value of the property.? When I checked this evening I expected to see that they were sold or converted to an REO.?
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1)? Did they change the auction date before bidding occured, or did it not meet its opening bid?
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2)? How many auctions does a property get and can you find out where in the process it is?
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3) Why would a property that is valued at nearly 500K, not be bid on with an opening bid of 73K?? (Auction was supposed to be today, and is now listed for tomorrow).
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Thanks in advance
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1 & 2 - Properties can be postponed up to 1 year with no additional notices recorded. After that they have to re-file.
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3. Could have been a second mortgage. When buying a second at auction, you are still responsbile for the 1st, delinquent property taxes and any other “senior debt”. You can read more about that in other posts in this forum.