The cleanup and investigation following an explosion at Quality Concrete in Dartmouth continued Tuesday.

Shortly before 3:30 p.m. on Monday, the roof blew off a silo at the plant.

It's unclear at this point what led to the explosion of the silo that contained fly ash which is used to make concrete.

“When it did let go, approximately 35 metric tonnes of ash was in the silo,” said Halifax Fire and Emergency deputy chief Roy Hollett. “It didn't all get out, but a considerable amount did get out when the container exploded. The top was found a couple hundred feet away on a car.”

Dust covered nearby vehicles and Halifax Water quickly covered catch basins in the area to prevent fly ash from entering the storm water system.

The company says there is no environmental impact from the incident.

Three people were treated for inhalation of dust, but remarkably nobody was taken to hospital,

“For a container that size to rupture and explode is very unusual,” Hollett said. “It doesn't happen a lot and at 3:30 in Burnside, people are leaving to go home, traffic lines are usually high along the streets and it is amazing no one was hurt.”

The Nova Scotia Department of Labour and Advanced Education is investigating.

They declined our request for an interview, but in statement said:

“A stop work order has been issued to Quality Concrete at this worksite as the investigation continues. We have no further information to share at this time.”

Quality Concrete has been in business since 1958 and a company official says this is the first time they've had a silo failure.

It's unclear how much it will end up costing.

“At the end of the day, we're just relieved that there were no injuries and that everyone is safe and just waiting until we can resume operations so we haven't really had any kind of financials on that,” said Tracey Tulloch of Quality Concrete.

The company has 17 other plants and they don't expect any delays in concrete production.

“Overall, we have other plants that can kind of take on anything that this particular plant was impacted by,” Tulloch said.

A stop work order will remain in effect until the investigation is complete.

The labour department says every investigation is unique and the length of each investigation varies.

They could not give an estimate on how long this particular investigation will talk to complete.

With files from CTV Atlantic’s Natasha Pace.