Copper wire thefts from highway street lights have decreased over the past few months following a December plea for help, an Indiana Department of Transportation official said Thursday.

Crews are crediting counter-theft measures put in place with the Indiana State Police, the Post-Tribune reports.

INDOT officials said in December that thieves were wearing helmets and safety vests and posting as highway workers as they wrested the copper off the base of the light poles. Thefts have been described as “very intense” along the Borman Expressway and Interstate 65.

Jim Pinkerton, an INDOT spokesman, said the department has spent $300,000 to $400,000 replacing lights, and officials are now exploring the possibility of solar lights.

Officials declined to give details on the measures being used to stop thefts, in order to keep crooks in the dark.