Police are trying to find out how the door of a house in Market Deeping was found open this month.
It happened in Baroness Way at about 3:15am last Tuesday but police believe no one got in.
Anyone with information should call 101, quoting incident number 185 of June 2.
Meanwhile, intruders are wanted by police after a burglary at a home in nearby Kingsgate between midnight and 6am on Tuesday, June 2.
Please call police on 101, quoting incident 36 of June 2 or Crimestoppers, anonymously, on 0800 555 111.