Police in East Lothian are appealing for information following a deliberate fire-raising in Prestonpans.
A property in Wilson Avenue was broken into and set fire to at about 0530 BST on Monday, causing £25,000 worth of damage.
The incident follows two other housebreakings in Prestonpans, which police believe may be connected.
All of the incidents, including the most recent, have occurred while the occupants have been on holiday.
Officers are warning people planning to take a break to secure their homes before travelling.
A police spokesman said: "We believe that whoever is responsible for these housebreakings has been aware that the occupants have been on holiday, and we are urging people who are planning a trip to make sure that all of the windows and doors on their property are correctly secured before they leave.
"At the same time, we are appealing for any information that can help us identify the suspect in each of these incidents, which we believe may be connected."
An address in Cameron Way was broken into sometime between 1300 BST on Sunday 25 July and 1900 BST the following day, where items were stolen and a fire was set.
In the other incident, which happened at a property in Kirk Street on Monday 19 July, a number of high-value electrical items were stolen, and the property was set on fire.