AP

A toppled construction crane sits on debris from a damaged building last fall in Bellevue, Wash.

BELLEVUE, Wash. -- A poorly designed crane base caused a Nov. 16 crane collapse in Bellevue that killed a Microsoft lawyer inside his apartment, according to an investigation by the state Department of Labor and Industries.

On Friday, officials announced the results of their six-month investigation. They found that the engineered foundation was designed to withstand only about a quarter of the pressure that the 210-foot tower required. They said the crane's base design wasn't standard and needed to be four times stronger to operate safely.

Steve Cant, a spokesperson for L&I, says the problem was compounded by the failure of the general contractor to maintain and inspect the crane base in accordance with the manufacturer's specifications.

The investigation found the crane operator was experienced and operating the crane properly.

Two firms are being cited for workplace violations, including Magnusson Klemencic Associates of Seattle, which designed the base, and Lease Crutcher Lewis, the contractor for the project.

Magnusson Klemencic released a statement Friday saying that the Department of Labor and Industries made several factual errors in its investigation. The firm plans to file an appeal.

The tower-crane accident killed a Microsoft lawyer who was in his fourth-floor condominium and damaged three buildings. The victim was 31-year-old Matthew Ammon, a patent attorney for Microsoft.

He had only worked there for five months, after moving from Kansas City. Ammon was originally from the Pittsburgh area, according to general counsel for Microsoft Brad Smith.