Savar, Bangladesh (CNN) -- Preliminary results of a government inquiry into last week's collapse of a nine-story building on the outskirts of Bangladesh's capital have found that "heavy machinery and high-capacity generators" were "largely responsible," according to state media.
"During the inquiry, we have found that use of substandard materials during the construction also contributed to the building collapse," committee head Main Uddin Khandaker told Bangladesh Sangbad Sangstha.
He predicted the committee would complete its report within a few days.
The preliminary conclusion came as police arrested engineer Abdur Razzak Khan on a charge of negligence, Bangladesh Sangbad Sangstha reported.
"He warned that the building was unsafe ahead of its collapse, but he worked as the construction consultant when the Rana Plaza's owner illegally added three floors" to the building, the agency said, citing a police official whom it did not identify by name.
Two other engineers -- who worked for the municipality of Savar -- have been arrested for having allegedly issued a safety clearance despite the appearance of cracks in the building that appeared the day before it collapsed, the news agency said.
The building owner, Sohel Rana, was arrested last weekend as he attempted to flee to India; owners and senior management of the factories have been arrested for forcing workers to resume production in the building shortly before it collapsed, it said.
The death toll from the country's deadliest industrial disaster rose Saturday to 547 as another 22 bodies were recovered, the agency said.
Authorities say more than 2,400 people have been rescued from the wreckage since the building collapsed more than a week ago in this suburb of Dhaka, the capital.
The number of dead has risen as workers have begun using heavy machinery to cull through the slabs of concrete, around which hundreds of people awaited news of the missing.
The collapse of the building that held five garment factories and thousands of workers has provoked widespread protests in Bangladesh, including attacks on some textile facilities. The demonstrators have expressed anger over the conditions in which many are forced to work.
But the trade group that represents the garment industry said Thursday it was safe for the millions of textile workers in and around Dhaka to return to duty.
Prime Minister Sheikh Hasina urged residents Friday to delay protests planned for this weekend in the capital so that government workers can focus on recovery efforts.
She told reporters she wanted the opposition alliance and Muslim hard-liners marching under the banner of Hefazat-e-Islam "to consider postponement, not withdrawal of their programs, at this critical point when the people are still fighting for life and rescue operations are under way."
Bangladesh's $20 billion garment industry accounts for 77% of the country's exports.
Among those caught up in the finger pointing after the disaster are Western retailers and clothing brands that Bangladeshi suppliers say put heavy pressure on prices, resulting in bad pay and conditions for workers.
The Bangladeshi government has come under criticism from representatives of labor groups who say it has failed to tighten lax safety standards despite a series of recent fatal disasters in the country's garment industry.
In an interview Thursday with CNN's Christiane Amanpour, Hasina acknowledged that the industry is beset with problems, but said her government is moving rapidly to fix them.
Journalist Farid Ahmed reported from Savar, and CNN's Tom Watkins reported and wrote from Atlanta.