As of late Wednesday night, electricity has been restored to more than 40,000 residents of Moore County, North Carolina, who’d been without power since Saturday evening. No information about possible suspects or motive has been disclosed at this time, but the FBI published a wanted poster Wednesday, and North Carolina Gov. Roy Cooper announced a $75,000 reward for information leading to the arrest and conviction of the person or people responsible for Saturday’s attacks.

The incident highlights a major vulnerability in the nation’s electrical grid, namely tens of thousands of substations throughout the country, many of which are in rural areas, and with varying levels of security. There have been attacks on substations in the past, most notably a 2013 attack in Northern California in which gunmen destroyed 17 transformers, causing $15 million in damage. The perpetrators were never caught.

Attacks on substations around the country have increased recently, leading federal law enforcement officers to issue a warning memo which was obtained by News Nation. It reads, in part:

Power companies in Oregon and Washington have reported physical attacks on substations using hand tools, arson, firearms and metal chains possibly in response to an online call for attacks on critical infrastructure. … In recent attacks, criminal actors bypassed security by cutting the fence links, lighting nearby fires, shooting equipment from a distance or throwing objects over the fence and onto equipment.

In addition, in mid-November a substation in Jones County, NC, a rural coastal county near New Bern, was sabotaged, leaving 11,000 customers (which is more than the county’s population of 9,255) without power for about two hours. The restoration timeframe was so much shorter in that instance because Carteret-Craven Electric Cooperative was able to reroute service around that substation.

However, there are a few important similarities between what happened in Moore County and what happened in Jones County. In the utility’s announcement, they noted:

The vandals damaged transformers and caused them to leak coolant oil. Crews worked quickly to stop the flow of coolant and contain it within the property.

In Moore County, a significant amount of oil was also leaking from equipment, at least at one of the affected substations. Southern Pines newspaper The Pilot reported Saturday night:

A reporter on scene at the Duke Energy substation off N.C. 211 near West Pine Middle School could hear and smell oil leaking from the facility.

An archived version of the same report contains a photo of police and Duke Energy employees at the same substation with the caption, “Police and Duke Energy workers survey damage to the West End substation Saturday night around midnight. Large power units were leaking significant quantities of oil.”

Now, transformers are filled with coolant oil, so if the body is shot up an oil leak is a logical consequence, and one that can cause the entire transformer to melt down and need replacement. Did the attackers just shoot at the largest piece of metal in front of them, or were they intending to completely destroy the transformer?

In addition, the attacks occurred at locations that are very close to significant military installations. The Jones County substation that was attacked is located in Maysville, which is about 30 miles from Marine Corps Base Camp Lejeune, the largest military base on the East Coast, and about the same distance from both Marine Corps Air Station New River and MCAS Cherry Point (as the crow flies, at least). As RedState noted in original reporting on the Moore County attack, the county is adjacent to Fort Bragg, a major Army installation that is home to the US Army Special Operations Command.

Jones County authorities have not disclosed the manner in which the Maysville substation was attacked, simply describing the act as “criminal vandalism.”

According to the North State Journal, electric grid security is going to be a top issue in the North Carolina General Assembly’s next session, and it should be a top issue for the next Congress, as well.