Two days after Tropical Storm Isaias caused devastation to much of the state, 10,813 Eversource power customers in Bristol were still without electricity as 8:30 p.m., according to the power company.
New Britain had 3,932 customers without power.
In area towns, Plainville had 3,879 outages and 2,331 customers in Plymouth were in the dark. Southington had 5,978 customers without power, Newington had 4,032 and there were 2,470 in Berlin.
Hundreds of more crews from out of state were arriving in Connecticut on Thursday to help restore power to nearly 500,000 homes and businesses that remained in the dark after the storm, as state officials announced an investigation into electricity utilities amid mounting criticism of their response.
Gov. Ned Lamont also announced Thursday that he deployed the Connecticut National Guard to help with power restoration.
A spokesman for the state’s largest electricity provider, Eversource, meanwhile, said there likely would have been many more outages if the company had not made hundreds of millions of dollars worth of upgrades under an agreement with the state following storms in 2011 and 2012 that cut power to hundreds of thousands of customers.
Eversource and United Illuminating said it could be several more days until power is fully restored. More than 590,000 outages remained in the state Thursday afternoon, down from about 611,000 during the late morning and down from more than 700,000 outages on Wednesday morning, the day after the storm.
The state Public Utilities Regulatory Authority, or PURA, announced Thursday it will investigate the utilities’ response to determine if they were adequately prepared, adhered to laws and regulations and whether civil penalties should be imposed. PURA also will look into failures of the utilities’ outage response systems.
Gov. Ned Lamont had requested an investigation Wednesday, calling the restoration efforts “wholly inadequate.” He also expressed confidence Thursday that all polling places will have power for Tuesday’s primary election.
“I think we’re going to be in good position by Tuesday, or else there will be hell to pay,” Lamont said.
Eversource said it was working on an estimate on when the majority of outages will be restored. United Illuminating said it expected to have the majority of outages restored Saturday and restoration substantially completed by Monday.
Eversource underestimated the severity of Isaias, but United Illuminating did not, said Marissa Paslick Gillett, chairwoman of PURA.
“There are disturbing reports emerging about the coordination, or lack thereof, between our electric utilities and the communities which they serve,” Gillett said. “This is simply unacceptable. There will be a full, transparent investigation.”
Criticism mounted against the utility companies on Thursday, in Twitter posts by government officials.
U.S. Sen. Chris Murphy, a Connecticut Democrat, called their response “unacceptable.”
In January 2013, state regulators approved a $300 million plan for Eversource’s predecessor, Connecticut Light & Power, to strengthen its electricity system to help avoid extended storm-related outages. Under the plan, the company trimmed scores of trees, strengthened utility poles and equipment and installed coated, thicker-gauge wire.
Eversource spokesman Frank Poirot said Thursday that those upgrades likely prevented scores of additional outages this week.
“The damage would have been much worse,” he said. “Despite the number of outages we experienced with this storm on Tuesday, I think there was still a benefit - a resilient and hardened electric system.”
Despite Eversource’s tree-trimming efforts, insects, disease and drought left trees across the state vulnerable to high winds, Poirot said.