UPDATE: High levels of carbon monoxide forced customers and employees inside at Walmart in Dayton to evacuate the building.

This Walmart has been undergoing renovations.

The fire chief says the equipment used may have caused a carbon monoxide leak

over the last few weeks, workers have been upgrading the inside of the Dayton Walmart.

Janet Roden visits regularly, and says the construction hasn't bothered her shopping experience.

“They are remodeling,” said Janet Roden. “They are putting in new flooring. They have been moving stuff around to remodel is what it looks like to me.”

The Dayton Fire Chief says a piece of equipment used for the remodel could have triggered the sensor.

He says Walmart managers decided to remove as much of those supplies as possible to make sure the store would remain safe.

“They were closing for 20 minutes,” said Roden. “So I've been sitting here waiting on them to open.”

Wednesday morning some shoppers were trying to get some groceries, or their prescription refilled.

Roden says the concern about the odorless substance still lingers

“My concern was the food in there, the clothing items and the other stuff,” said Roden.  “Is that all right? Was anything contaminated?”

“No one was hurt because of this leak,” said Roden.  “Right now we're not sure where they stand with renovations.”

Carbon monoxide can cause a headache, dizziness, nausea and shortness of breath, but officials say customers and employees were not in Walmart long enough to feel those symptoms.

PREVIOUS STORY: Rhea County dispatchers confirm Walmart in Dayton, TN has been evacuated due to high levels of carbon monoxide.

The store is open 24 hours, but it's not yet clear how many customers or employees may have been affected.

We have a crew en route.

This is a developing story and will be updated.