Six people are in a stable condition in hospital after part of a building collapsed in Belfast.
Eyewitnesses said a floor gave way as concrete was being poured onto the top of a six-storey office block under construction in Victoria Street.
They said some workers fell about 30ft and had to be pulled free from falling steel girders, scaffolding and rubble in the accident on Monday at 1040 GMT.
The workers suffered broken bones in the accident.
It is believed that up to 60 people were working on the site at the time of the accident.
Fire Service used specialist dogs to search the rubble, but no-one else was found.
The accident is to be investigated by the Health and Safety Executive.
May Street has now reopened, although Victoria Street remains closed and police have advised motorists to avoid the area if possible.
Nine fire engines and a specialist fire crew, as well as ambulances crews and police officers attended the scene.
The accident happened close to the back of the Royal Courts of Justice in the centre of Belfast where new offices are being built for the Northern Ireland Law Society.
Brendan Collins, 23, was beside the building when the scaffolding crashed to the ground. "It looks like the supports underneath the building gave way, which caused machinery to fall on top of the workers.
"I helped to rescue them. I ran in with four or five other fellas and lifted the machinery off one of them. He was covered in blood and completely crushed."
A workman said: "I was in the cellar at the time. It was like a bomb going off. We all ran. It was all rubble. We helped the men that were trapped. It was all we could do. I'm in a state of shock myself."
Kris Mills, who works nearby, told BBC News that he was outside at the time and heard a loud crash.
"I saw them pulling two people out who just looked in shock, but as soon as emergency services arrived we were moved back from the scene," he said.
In a statement, Turkington Construction which was working on the site, said it "deeply regrets the incident which took place today at Law Society house.
"We are now working closely with the Health and Safety Executive to investigate the causes of the incident and to ensure the site is secured to the public and our workforce."
Alan Hunter, chief executive of the Law Society, said: "We were shocked to hear of the accident at the building site.
"We don't yet have details of what happened but we understand six people have been injured. We wish all those who have been hurt a speedy recovery."
First Minister Ian Paisley has expressed his sympathy to those injured in the building collapse and to the children involved in the bus crash in County Tyrone which also happened on Monday.