Gathered in front of the ruins of a precision mechanics factory near Modena, colleagues of three workers killed in Italy's quake on Tuesday said they had "no tears left" to mourn.

Huddled in groups at the gates of the devastated Meta factory, those who managed to escape with their lives had been there since the quake hit at 0700 GMT, causing widespread destruction across the region and killing at least 15.

The powerful tremor tore through the brink hanger, ripping the building in two just an hour after the 20 or so workers had started their shifts, sending them running in terror for the exits as masonry fell around them.

"I'm grief-stricken, speechless. I have no tears left to shed," said one worker called Daniel, who said he had known the men who were killed for years.

Another described what a blow it was to the family-run business in San Felice sul Panaro, where everyone knew each other so well.

As the dust began to settle in the moments following the quake, those who had made it to safety realised three people -- an Italian as well as an Indian and a Moroccan called Kumar and Mohammed -- had been killed in the collapse.

"Everything happened so fast, in about seven to eight seconds. I don't even remember. I ran out carrying the piece I was working on and I saw everything crumble," said Daniel, who has worked for Meta for over a decade.

"The quake was so violent," he said, trembling with shock, and adding that he had feared being trapped in the shaking building.

Friends of Kumar and Mohammed who had run down to the factory site on hearing the news, joined the workers in paying their respects.

Sikh Pal Surinder said he had grown close to Kumar in the tent camp where they had been living since the first quake hit the region on May 20, killing six and damaging and weakening buildings -- many of which then toppled Tuesday.

In both quakes, the majority of victims were workers, and there were reports circling that many of the factories which were damaged in the earlier quake were opened again too quickly, before thorough checks had been carried out.

One worker at Meta said Mohammed had told him he was afraid to go back to work, saying: "They are making us work while the building has cracks in it."

But the rumours were denied by the victims' colleagues, who said they had all been keen to return to work and "no one was afraid."

"The hangar had not been damaged. They had carried out checks, security controls," Daniel said.

In the face of tragedy, as they prepared to leave the site and spend the night in temporary camps along with thousands of other homeless, the workers said their boss was not to blame and he had risked death alongside them.

"Our boss was inside. Rubble fell on him, he was bleeding... The engineer who died was standing just next to him," Daniel said.