Officials say workers were doing electrical work on the elevator in the office building hours before an advertising executive was caught in its doors and crushed to death.
That electrical work is now the focus of the investigation into the death of 41-year-old Suzanne Hart.
The Madison Avenue building remains closed.
The city's Department of Buildings says the force of the accident was so severe, it has raised concerns about the building's structural integrity. Engineers are looking into the matter.
Inspectors also plan a citywide check on all elevators serviced by the maintenance company, Transel. Its workers had serviced the faulty elevator just hours before Hart's death.
"This is every family's worst nightmare," Hart's father, Alex Hart, said. "There's no easy way to deal with it."
Transel reportedly maintains elevators at nearly a dozen major buildings in the city. The company's website lists the Graybar Building, Carnegie Hall and The Plaza Hotel, among others.
"Things happen in life," Alex Hart said. "We don't know why, and we don't know how we deal with them, but we do."
Transel has hired a PR firm to represent the company. They issued a statement Thursday saying they are cooperating with the investigation and that their thoughts and prayers are with Hart's family.
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