Workers with Lewis Tree Service and SCE&G remove a tree from the middle of President Street in downtown Charleston on Tuesday morning. The power company said it could take days to restore power to the tens of thousands of customers on the coast after Tropical Storm Irma. Leroy Burnell/Staff

Tens of thousands of people across South Carolina were still in the dark Tuesday, and power companies from the Lowcountry to the Upstate were gearing up for a recovery effort expected to take days longer.

Bands of wind and rain from Tropical Storm Irma knocked out electricity to homes and business in the largest series of outages the state has seen since Hurricane Matthew battered the coast last fall.

As of 5 p.m. Tuesday, utilities reported that 121,000 of their customers in South Carolina were without power. Most of the remaining outages were in the Upstate, where wind gusts and falling trees knocked down power lines.

Across the state, most people who lost power had it restored after outages peaked at about 275,000 Monday night.

In the Lowcountry, utility officials cautioned that a sprint of progress didn’t mean the state’s damaged electric grid would bounce back overnight. The remaining outages, they say, will likely take longer to resolve, especially in remote and lightly populated areas.

South Carolina Electric & Gas said it had restored power to more than two-thirds of the roughly 155,000 customers who lost it at the storm’s peak. But some will likely be in the dark until the weekend, said Keller Kissam, the Cayce-based utility’s president of retail operations.

Most of the lingering outages on SCE&G’s system, which reaches from the Midlands to the Lowcountry, came from the coast. Charleston and Beaufort counties accounted for half the outages.

Several lines will have to be rebuilt, Kissam said, work that could take another three to five days. Many of the remaining outages affect only a few customers each, making it harder to bring homes online en masse.

"It will slow down," Kissam said. "You still have to go there and work just as hard and sweat just as much to get them back on. But you don’t get as many customers back on for the gallons of sweat that you’re putting out there."

For the most part, the arteries of the electric grid appeared to be up-and-running again after sustaining some damage. Santee Cooper, the state-owned utility, had problems on five of its transmission lines, including a few that carry electricity from power plants to local cooperatives. All of them were back in service Tuesday, spokeswoman Mollie Gore said.

The problems tend to crop up as the power is delivered to local distribution system. The state’s electric cooperatives reported thousands of outages in the Upstate, and Berkeley Electric Cooperative said thousands were without power in western Charleston County.

In the Charleston's tri-county area, SCE&G and Berkeley Electric reported about 15,000 outages by late afternoon Tuesday.

Sign up for our new business newsletter

We're starting a weekly newsletter about the business stories that are shaping Charleston and South Carolina. Get ahead with us - it's free.

Lou Green, a spokesman for the co-ops’ trade group, said it wasn’t yet clear when electricity would be restored statewide.

Likewise, Duke Energy, the state’s largest power provider, said it expected a "multi-day" effort to restore power in Greenville and the northwest corner of the state, but it didn’t yet have a firm timeline.

"Most of the damage is what you would expect from tropical storm force winds — trees down, poles damaged, lines down," Duke spokesman Ryan Mosier said in an email. "It does make repairs more time-consuming because you have to remove the trees to make the situation safe before you can rebuild the infrastructure."

The flurry of work to mend the state’s electric grid was complicated in part by the breadth of Irma’s damage. The storm’s bands scraped across the state, and it left a trail of destruction in Florida and Georgia, too.

Some South Carolina line workers headed to Florida to start returning power to the millions of customers who lost it, SCE&G said, while crews from around the country drove in to take their place.

SCE&G says convoys of workers were headed to South Carolina from Alabama, Indiana, New York and Texas, while the co-ops expected help from Arkansas, North Carolina and Virginia.

Reach Thad Moore at 843-937-5703. Follow him on Twitter @thadmoore.