The city's Department of Buildings says engineers have found defects in the hoisting system of the crane that crashed down at the No. 7 subway line extension construction site, killing a 30-year-old worker from New Jersey.
The Buildings Department said Thursday that maintenance and operation of the crane prior to the incident has become the focus of their investigation.
The rig, which failed Tuesday night, had been inspected most recently by the Buildings Department on Jan. 10. The MTA said that inspection could not be completed because the rig was in operation at the time.
At least one of the cables that hadn't been checked during that inspection snapped in Tuesday evening's accident, officials said.
A follow-up inspection had been scheduled for Thursday.
The crane involved in the accident was last fully inspected in July and received a "satisfactory" rating on all points.
The MTA suspended work on the lower Manhattan site after the tragic accident and ordered re-inspections of all cranes at agency work sites. The MTA said all cranes passed inspection, according to The New York Post.
The incident marked the city's third fatal crane accident in four years, and followed a series of scandals involving lax or corrupt oversight of the industry.
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After a pair of catastrophic crane accidents crushed buildings and killed nine people in 2008, city officials did a major overhaul of the rules and safety procedures for cranes.
The rig at the subway tunnel site was exempt from most city construction safety rules because it was working for an independent state authority.
The MTA said it was weighing a proposal by City Council Speaker Christine Quinn to place all of its construction activity under the authority of the city's Buildings Department.