A woman was stunned to return home to find 107 gnomes carefully arranged on her front garden.
Police were called at about 1.30am on June 2 after the woman found the gnomes including a formation 30 rows deep and three abreast.
Officers are now investigating the incident, which took place at Bowdens Park in Ivybridge, Devon, between 9.30pm on June 1 and 1.30am the following day.
A local garden centre has been checked but no gnomes have been reported missing, a spokesman for Devon and Cornwall Police said.
The incident is treated as "found property" and residents are being urged to check their gardens to see if any gnomes have disappeared.
"Someone has taken quite a bit of time and effort to place them there," the force spokesman said.
"It has unsettled the home-owner who has no idea why there were put in her front garden at night.
"We are seeking to establish where the gnomes have come from.
"The question is whether they are stolen, or if it's a prank and someone is playing a game of gnomes."
Anyone with information is asked to contact the force on 101 quoting police log number 27 of 2/6/2015.