Watch: Nashville tornado hit Madison power station causing fiery explosion.

A fiery explosion captured on video as a tornado tore through Madison, Tennessee, showed the storm's direct impact on a Nashville Electric Service substation, the utility confirmed Monday.

The tornado's path from Davidson County's western boundary through Sumner County also struck another substation in Hendersonville and a 500,000-volt tower operated by the Tennessee Valley Authority, and damaged more than 150 poles.

It's the first time since the early 1970s that two NES substations have suffered direct hits from a tornado, and the damage is "substantial," Brent Baker, NES vice president and chief customer and innovation officer said Monday.

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About 5,500 customers remained without power as of Monday afternoon, down from 48,000 experiencing outages on Saturday. More than 300 crews and NES staff members have been working around the clock in extreme temperatures with assistance from crews from Georgia, Kentucky, and Indiana since then, Baker said.

But because the damage to both substations, transmission equipment, and power line poles is extensive, it will likely be "toward the end of the week" before power is restored to every customer, NES Vice President of Power Systems Operations Jack Baxter said.

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What caused the explosion?

Debris striking the two NES substations caused the most damage, particularly to the Hendersonville substation.

In Madison, some structures inside the North substation failed, poles went down and debris impacts caused a breaker explosion, producing the fireball seen on live footage, Baxter said.

The North substation is a transmission substation and does not directly serve any customers. It has a 161,000-volt line that feeds part of the DuPont facility in Old Hickory.

The Hendersonville substation does serve customers and has been a main priority for repair, Baxter said.

"Really the focus Saturday night and through yesterday was to get the transmission lines back intact that fed the Hendersonville substation and make repairs within that substation," he said.

Ongoing repairs

Because NES operates more than 60 substations throughout its coverage area, the utility keeps materials and equipment on hand to make repairs, but Saturday's damage surpassed typical repair needs. Middle Tennessee Electric provided NES with some materials necessary for Hendersonville repairs.

TVA is responsible for repairs at their damaged tower.

Because the system is interconnected, the tornado's path crippled multiple parts of NES' infrastructure, Baxter said.

"If we had just a quarter of a mile deviation in that path either way, we would not have had any of the substation damages … and it could have missed some of our key transmission facilities also," he said. "The substation work this time has been a challenge."

The storm initially caused power loss at eight substations due to damaged transmission infrastructure. Within a few hours, NES rerouted power and reduced the number of down substations by half.

At the last count, 156 poles were broken, including 25 transmission lines. In a single section of Gallatin Road in Hendersonville, 29 poles were broken. NES uses poles designed to withstand winds up to 110 miles per hour, but debris can cause further damage, Baxter said.

Multiple crews are digging holes to replace poles and repair downed lines.

In the meantime, Baker urged customers without power to be cautious of downed power lines and poles, and to assume all downed lines are live and call 911.

Anyone using a portable generator for power should make sure it is outside and not connected directly to the home's electrical wiring. If a customer has physical damage to the home's electrical systems, Baker said to call an electrician to get it fixed so power can be restored to the home as soon as possible.

This article originally appeared on Nashville Tennessean: Tennessee tornado hitting Nashville power station caught on video