More than 160 Maui Electric Co. workers and two contracted crews responded to the county’s biggest power outage in more than a decade early Tuesday morning in the wake of a thunderstorm that rolled through Maui County, a utility official said Wednesday.

The vast majority of the more than 66,000 customers who lost electricity had power restored as of 10 p.m. Tuesday, MECO spokeswoman Shayna Decker said. She said crews continued working on individual pocket restorations.

MECO currently is doing a assessment of the outage, she said. Nearly the entire county went dark around 2:50 a.m. after a severe thunderstorm with heavy rain, powerful winds and lightning rolled through Maui County.

The thunderstorm toppled a main transmission line and two poles at Hana Highway and Hookele Street, Decker said. She said lightning struck electrical systems across the island causing the frequency of energy on the system to drop suddenly and to cut power to customers.

“We don’t know how many times our equipment was struck, but it’s been reported that there were thousands of lightning strikes over Maui during the storm,” Decker said. “Typically, if lightning makes contact with electrical equipment, it can result in the equipment — such as transformers or fuses — to overload and break.”

By 6:30 a.m. Tuesday, most of the island’s critical infrastructure, such as the police department, hospitals and airports, were back online. By noon, crews restored about 65 percent of customers, and by 4 p.m., 98 percent were back online, she said.

Crews worked through the evening to repair damaged electrical equipment and downed power lines and to maintain adequate power generation as areas of the island came back up in phases throughout the day, Decker said.

“This step in restoration is a delicate process as we’re systematically restoring circuits in various geographical areas on the island,” she said. “This is done to maintain the balance between current energy demand, or customer usage, and available power generation that we deliver to our customers.

“The restoration process does take time, so we appreciate our customers and community for their continued patience as we safely worked to bring everyone back on.”

Maui’s last major islandwide power outage was in October 2006 after a 6.6-magnitude earthquake off the Big Island collapsed bridges, closed roads and caused an estimated $200 million in damage statewide. Power was restored to all customers after about nine hours.

Decker said MECO has protective lightning arrestors installed throughout the system to help prevent widespread power outages, but “it’s hard to predict what Mother Nature is capable of in these situations.”

“As part of our ongoing efforts to further modernize and harden our electrical grid, we continue to work on pole replacements and transmission line upgrades to make our electrical system more resilient,” she said.

MECO also is working to restore electricity to the Koali area of Hana, according to the county Department of Water Supply. Due to the lack of electricity, the booster pump in the area is not functioning so the department is requesting all customers in the area to conserve water until 10 a.m. today.

MECO said a tree fell on power lines in the area at about 6 p.m. Tuesday.

For any water related problems or questions, call the department’s 24-hour service at 270-7633.

Haleakala National Park reported reopening the back country summit area for tent and cabin camping permits, officials said.

Hosmer Grove campground and trail also reopened at 1 p.m. Wednesday. Pipiwai Trail and the roads to the Kipahulu District are open, as well.

* Chris Sugidono can be reached at csugidono@mauinews.com.