Around 800 homes in a village near Lincoln were plunged into darkness after almost two kilometres of power cables were stolen overnight.
The incident took place on land between Burton Village and Burton Waters, on the outskirts of Lincoln, at around midnight on October 4.
Lincolnshire Police believe the thieves accessed the area via North or South Scarle and used a dinghy to cross a drain and reach a wooded area where they disabled the power supply.
They then cropped around 1,800m of cable and left the scene, leading to a power blackout to around 800 homes in the Burton Waters area.
Officers say the thieves clearly planned the offence and may have been in the area earlier that day, or over the last couple of days.
They would have needed a fairly large vehicle to transport the cabling.
Third village hit by cable theft
This is the third time this type of crime has been committed in Lincolnshire in recent weeks, Lincolnshire Police said.
A similar incident was reported in Newton-on-Trent earlier this week and another at Normanby-le-Wold at the end of August.
Inspector Simon Outen said: “This is an extremely dangerous crime.
“These cables carry 11,000 volts of electricity and there have been a number of deaths across the country this year where people have tried to do something similar.
“This crime has also caused significant disruption to the local community, which is totally unacceptable.
“We are appealing for anyone who sees any suspicious vehicles in fields in the county to call us immediately with descriptions.
“The only people who should be working on power lines are Western Power Distribution staff. They use white vans with the company name on the side.
“Any other vehicle seen near power lines in fields should be reported to us.
“If anyone does have any information they think will help us then please get in touch as soon as possible.”
Western Power Distribution is offering a £5,000 reward via Crimestoppers for information leading to a conviction in relation to these crimes.
Anyone with information can call Lincolnshire Police on 0300 111 0300 or anonymously to independent charity Crimestoppers on 0800 555 111.