Thieves made off with jewellery, ornaments and a safe after burgling a house in Station Road, Long Sutton.
It happened some time between 6pm on October 24 and 3.15pm on October 25 when thieves got through the patio doors of a conservatory before forcing their way into the house itself.
Police are also investigating a burglary outside Spalding Grammar School after two sheds and an outbuilding were found last Sunday to have been broken into.
Anyone with information should call 101, quoting incident numbers 275 of October 25 and/or 165 of October 28.