An investigation was underway Monday after a building collapse in Brooklyn that morning claimed the life of a construction worker and injured several others.

Fire officials say the building located at 227 Carlton Avenue in Fort Greene collapsed just before 9:15 a.m.

The four-story building -- a former horse stable for a church next door -- was under construction at the time of the collapse.

"Very sad. Not only thinking about it but to see something in your vision. It is very troublesome," said Ignatius Ragis, a construction worker at the site.

Ragis, who has been doing construction for 35 years, says he knew there could be trouble when he saw a new load of cement blocks being lowered to the roof from a truck on the street. He says he knew the top floor had all the weight it could hold and says his supervisor tried to stop the delivery but the truck operator and the foreman four stories down could not hear him.

"When they were delivering the last bit of cement. The supervisor was there. You felt a tremble and tried to stop the guy but it was too late," Ragis said.

"It was either in the act of the delivery or immediately following and in either case the floor it was being delivered on. It is clear it was not structurally stable and couldn't handle the load," said Department of Buildings Commissioner Robert LiMandri.

Officials at the scene say during the collapse two workers fell from the fourth floor into the basement where they were trapped.

One of the workers, identified as a 67-year-old man, died.

The other was rushed to a nearby hospital in critical condition.

"I thought a truck overturned in the street and then I started hearing tons and tons of firetrucks and fire engines," said Pierre Degaillande, a neighbor.

"I was getting ready and heard a big boom. I looked out and you could see them craning cement block in and out of the roof and looked out and all of the floors were collapsed so it looks like one of the pallets of blocks slipped off when they were craning it," said Michael Hartman, a neighbor.

Work at the site was suspended Monday.