Investigators look down a hole where two workers fell on Wednesday in a construction mishap. One man died after a concrete slab fell on him. Giacomo Panico/CBC

Investigators remain on the scene of a construction site in the Sandy Hill area of Ottawa where a 50-year-old man was killed after a slab of concrete fell on him.

Co-workers at Hoskins Restoration Services on Albion Road said Ben Long was a hard-worker who took his job seriously, but was also a joy to be around.

Long spent most days assigned to drive the company's supply truck, but also did masonry work. On Wednesday, he was jack-hammering a concrete porch at a house on Marlborough Avenue when it collapsed.

He and another worker plunged four metres and into a cold-storage room below.

"When [the foundation] basically gave way, two of the workers went down into the hole, and the concrete slab followed suit and landed on top of them," said Marc Messier, Ottawa Fire spokesman.

Co-worker breaks leg in fall

Long was transported to hospital without vital signs and was pronounced dead upon arrival.

His 36-year-old co-worker was treated for a broken leg.

Investigators from Ontario's Ministry of Labour are working with City of Ottawa inspectors and two of the project engineers to assess the scene and try to determine what happened.

Project engineers said the crew had been assigned to do basic renovation work, including re-doing the concrete porch of the home, which was built in 1905.

Even before the death, the masonry company had been facing a difficult year. In November their office was the target of an arson attack. No one was injured, but the office building is boarded up and the company is operating out of a trailer in the parking lot.

A Quebec man was charged with arson and possession of incendiary material in that incident.