Thieves with a lot of brass ripped copper ground wire from a National Grid substation, causing power problems in North Providence earlier this week and leading to the shutdown of electricity to 5,000 customers in four communities after the company discovered the damage Thursday and scrambled to make repairs.

Spokesman David Graves said it appears that the theft was ongoing. Workers who arrived at the substation Thursday found much of the wire yanked out and some of it rolled up, waiting to be taken away.

“The danger anyone places themselves in doing something like this is absolutely ridiculous. It’s beyond foolishness. It’s almost suicidal” because the wires in the substation carry tens of thousands of volts, said Graves. The ground wire might not be live, but manipulating it could cause a deadly electric arc.

Graves said it will not be known how much copper wire was copped until Friday, at the earliest. “Our concern today was to make the system safe and maintain service to our customers.”

The emergency repairs to the Smithfield substation, just off Route 44 near Route 295, affected North Providence, Johnston, Smithfield and Scituate.

The company originally planned to shut off all 5,000 customers served by the facility, but instead opted for rolling blackouts — affecting 1,000 to 1,500 customers at a time — as portions of the substation were repaired.

The theft was discovered after the company received a call of flickering lights in North Providence.

“We went out this morning and replaced a regulator,” Graves said. That caused about 2,700 customers to lose power for an hour or so. “Then we did a further inspection at the substation and found that some ground wire had been removed, and other wire had been rolled up, like it was being prepared for theft,” said Graves. “Once pulled out of the ground, it creates an imbalance in the system, which caused the flicker.”

Smithfield and state police have been called in to investigate. National Grid also has a group of police departments and security organizations that specialize in investigating the theft of equipment from utility companies, Graves said.

gemery@projo.com