By Greg Argos

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PHILADELPHIA (CBS) — One year after an inferno tore through several buildings in Old City, authorities say it was intentionally set. The fire brought the vibrant section of the city to a standstill for months.

It’s been a difficult year for those living and those working near 3rd and Chestnut. This once bustling Old City corner is still in recovery.

Many businesses remain closed almost a year after a four-alarm blaze tore through 239 Chestnut and damaged buildings on both sides of it.

“It’s been under construction. And this has been a sort of black hole here. It’s been a sore spot for the entire year and probably another six months to come,” Andre Peruzzi said.

Friday afternoon, the ATF confirmed the cause of the blaze is arson. No arrests have been made.

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Peruzzi, who lives a half block away, perhaps best summed up the reaction of many.

“It’s horrible. I can’t believe someone would do that, put many many lives in danger,” Peruzzi said.

The same sentiment is felt by business owners on the next block.

“I really don’t think anticipating it would really, truly be ruled in that way,” Liz Sieber said.

Sieber owns the Omoi Zakka Shop, a gift store on 3rd Street, slightly north of the building that burned.

“Replaced the ceiling, replaced the walls and refinished all the floors,” she said.

All due to massive water damage that closed her business for four months.

When she reopened, Sieber says the community has helped her business stay that way.

“The neighbors have been wonderful,” she said. “Everyone has been really supportive and making sure to come down on this block.”

But on Chestnut, many businesses remain shuttered.

A pizza shop permanently closed its doors in the months following the blaze. 239 Chestnut’s direct next-door neighbor, a hotel, is still deemed unsafe.

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The only shop open is Xenos, which sells souvenirs.

Owner Tina Hu has operated the business for 32 years and says she has no other option than to keep the doors open.

“You do your best. I need to survive. I need to show up,” she said.

The ATF says it’s still investigating the blaze.

They’re asking anyone with information to call their Philadelphia field.