(Bloomberg) -- More than 33,000 homes and businesses remain without power in North Carolina after two electrical substations were damaged by gunfire in what authorities are calling an intentional attack.

The FBI is investigating the assault which left “extensive damage” to the substations in Moore County, North Carolina. The destruction was discovered around 7 p.m. Saturday evening, county sheriff Ronnie Fields said in a news conference Sunday. About 45,000 people were plunged into darkness and a county-wide 9 p.m. curfew was implemented Sunday to protect citizens and businesses.

The attack was an “intentional, willful and malicious attack,” state Senator Tom McInnis said during the news conference. “The perpetrator will be prosecuted to the fullest extent of the law,” he added.

Power may not be completely restored until Thursday, utility Duke Energy Corp. said in a statement, adding that it was repairing multiple equipment failures.

The attack comes amid growing concern from federal officials about the vulnerability of the nation’s power grid to terrorism and the security of key pieces of equipment. Substations are critical links to the nation’s transmission systems yet are typically left unguarded.

A sniper attack in 2013 knocked-out a PG&E Corp. electrical substation that powered California’s Silicon Valley for 27 days. 

A motive for the attack remains unknown, North Carolina Representative Richard Hudson said in a statement Sunday. 

Fields said authorities were investigating if there was a link between the attack and protesters of a local drag queen show, though no evidence had been found tying the two.

Energy Secretary Jennifer Granholm said she’d be in contact with the utility, and the agency’s Office of Cybersecurity, Energy Security, and Emergency Response was working with other federal departments on the incident. 

--With assistance from Josh Saul.

(Story updates with number of outages Monday morning in first paragraph.)

©2022 Bloomberg L.P.