CARTHAGE, N.C. >> Two power substations in a North Carolina county were damaged by gunfire in what is being investigated as a criminal act, causing damage that could take days to repair and leaving tens of thousands of people without electricity, authorities said Sunday.

In response to ongoing outages, which began just after 7 p.m. Saturday across Moore County, officials announced a state of emergency that included a curfew from 9 p.m. Sunday to 5 a.m. Monday. Also, county schools will be closed Monday.

“An attack like this on critical infrastructure is a serious, intentional crime and I expect state and federal authorities to thoroughly investigate and bring those responsible to justice,” Gov. Roy Cooper wrote on Twitter.

Moore County Sheriff Ronnie Fields said at a Sunday news conference that authorities have not determined a motivation. He said someone pulled up and “opened fire on the substation, the same thing with the other one.”

“No group has stepped up to acknowledge or accept that they’re the ones that done it,” Fields said, adding “we’re looking at all avenues.”

The sheriff noted that the FBI was working with state investigators to determine who was responsible. He also said “it was targeted.”

“It wasn’t random,” Fields said.

Fields said law enforcement is providing security at the substations and for businesses overnight.

“We will have folks out there tonight around the clock,” Fields said.

More than 41,000 electric customers in the county remained without power on Sunday afternoon, according to poweroutage.us.

With cold temperatures forecast for Sunday night, the county also opened a shelter at a sports complex in Carthage.

Duke Energy spokesman Jeff Brooks said multiple pieces of equipment were damaged and will have to be replaced. He said while the company is trying to restore power as quickly as possible, he braced customers for the potential of outages lasting days.

“We are looking at a pretty sophisticated repair with some fairly large equipment and so we do want citizens of the town to be prepared that this will be a multiday restoration for most customers, extending potentially as long as Thursday,” Brooks said at the news conference.

Dr. Tim Locklear, the county’s school superintendent, announced classes will be canceled Monday.

“As we move forward, we’ll be taking it day by day in making those decisions,” Locklear said.

The Pilot newspaper in Southern Pines reported that one of its journalists saw a gate to one of the substations had been damaged and was lying in an access road.

“A pole holding up the gate had clearly been snapped off where it meets the ground. The substation’s infrastructure was heavily damaged,” the newspaper reported.

The county of approximately 100,000 people lies about an hour’s drive southwest of Raleigh and is known for golf resorts in Pinehurst and other communities.