Thieves stole 22,000 feet of copper cable from a tunnel inside the elevated light rail track between Seatac and Seattle, Sound Transit said Friday.
The 70,000 pounds of copper has a street value of around $250,000.
"Our best evidence is ...it was cut down into into chunks...50-60 pounds a piece...then carried out," said Ron Griffin, chief of the Sound Transit police force.
"There's no danger to the trains or passangers with this being missing. What it does is protect the structure from any stray currents," said Sound Transit's Bruce Gray.
Sound Transit believes that by now the copper has been sold to a metal dealer. The agency is asking the public to contact the King County Sheriff's Office if they have any information about the crime.