(Bloomberg) -- Investigators still don’t know who shot at two electric substations in North Carolina over the weekend and knocked out power for about 45,000 homes and businesses, authorities said Tuesday.

“Our investigation continues at a very fast pace,” Moore County Deputy Chief Richard Maness said during a media briefing. He added that his department is working with the Federal Bureau of Investigation and the State Bureau of Investigation, and that the tip line has been very active. “We are looking at every angle.” 

Moore County Chairman Nick Picerno called out to the attacker directly. “Whoever the perpetrator is, I hope they turn the power off in the cell they put you in,” he said.

About 35,000 homes and businesses remained without electricity Tuesday afternoon, according to a statement from utility Duke Energy Corp. Power should be restored to nearly all customers by 11:59 p.m. Wednesday, the company said.

“We have made very good progress today,” Duke representative Jeff Brooks said at the news conference. “You will see waves of customers coming on, a few thousand at a time, as we work to restore power to the grid.” 

When asked Tuesday if he knew who was behind the incident, President Joe Biden told reporters: “No, we don’t yet. I’m running that down, I got a brief this morning.”

Experts say the outage highlights the fragility of the country’s power grids. While such networks are regular targets of cyberattacks, major physical assaults on the systems are rare. The incident in North Carolina underscores how, when successful, such strikes can have widespread consequences.

(Updates with quotes and information from news conference throughout.)

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