The pins that hold sections of crane together appear to have been removed from the black connecting sleeves, upper right, causing a fatal collapse in Seattle's South Lake Union area in April. The occupants of this car survived, though four other people perished in the collapse.

TUKWILA — State authorities have faulted three companies for April’s deadly crane collapse in South Lake Union, finding that workers prematurely removed pins and left the tower vulnerable to a gust of wind that brought it crashing down over one of Seattle’s busiest streets.

Workers from several companies were disassembling the crane used to build Google’s new campus when it collapsed on April 27, killing four people. The catastrophe brought home with shattering force the potential hazards of the tower cranes that have become a fixture of the city’s skyline and construction boom.

Officials with Washington state’s Department of Labor and Industries stressed at a briefing that most tower cranes are operated safely, but indicated the practice of prematurely removing the pins may not be an isolated event. State officials acknowledged, however, they don’t have a way to compel companies to abandon this practice — which can speed up disassembly but jeopardizes a crane’s stability — and they are considering new regulations.

Separate from the state investigation, the Seattle Police Department confirmed Thursday it is conducting a criminal investigation into the accident.

The collapse killed Alan Justad, 71, a former city planning official, and Sarah Wong, a 19-year-old Seattle Pacific University student, who were in separate cars when the crane crashed down on Mercer Street. Ironworkers Andrew Yoder, 31, of North Bend, and Travis Corbet, 33, were working on the crane and died after it plunged to the street.

Justad’s three daughters said they were devastated by the findings.

“There is no acceptable reason for why our beloved father is not with us today,” Jade, Marika and Miro Justad said in a statement. “Corners were recklessly cut and as a result, four lives were lost. We will carry this tragedy with us forever.”

The state cited general contractor GLY Construction, which had leased the tower crane, for three serious violations, including the failure to adequately supervise the disassembly. The company was fined $25,200.

L&I also faulted Northwest Tower Crane Service, responsible for dismantling the crane, for failing to follow manufacturer procedures in prematurely removing pins, not giving its crew adequate instructions and not ensuring that the workers were trained in guarding against a collapse. The company was cited for three serious violations and fined $12,000.

The regulator came down hardest on Morrow Equipment, which supplied the crane and had the greatest expertise in disassembling it. The company didn’t ensure that the technician overseeing the disassembly followed manufacturer procedures in ways that “directly contributed to the collapse.”

Morrow was cited for a “willful” serious violation, indicating it ignored a legal requirement or was indifferent to employee safety, according to L&I, and fined $70,000.

L&I did not cite two other companies involved, Omega Morgan and Seaburg Construction.

“The incident that occurred was totally avoidable,” Joel Sacks, director of L&I, said Thursday. “If the companies on site had followed the rules that were in place, the crane would not have fallen and four people would not have lost their lives.”

Ted Herb, the president of GLY Constructi=on, said his company is “actively reviewing” the new report and will use its findings to “do everything possible to protect our workers and the community.”

“We have already made changes to our systems and implemented protections based on immediate key learnings from the event, and we remain committed to upholding strict industry safety protocols at all of our jobsites,” Herb said in a statement. “The impact of this event will be felt for some time and we will use it to strengthen and safeguard our employees and the communities in which they work.”

John Morrow, chairman of Morrow Equipment, said in a statement that the company “respectfully disagrees with the citation issued,” But he declined further comment out of respect for the families of those involved in the collapse.

Northwest Tower Crane didn’t respond to requests for comment.

Tower cranes comprise 20-foot steel sections, held together by connecting pins and sleeves.

Typically, experts say, a tower crane is dismantled in sections, with ironworkers unpinning or unbolting a section as a smaller crane lifts it off, starting from the top. The process is then repeated — hook, unpin, lift — until the entire crane is dismantled.

Crews are not supposed to remove pins from a section until the assisting crane has hooked it. At the work site in South Lake Union on April 27, however, workers had removed more than 50 pins from “the entire length of the structure,” said Brian Haight, L&I’s crane-certification supervisor, leaving only one pin in place.

“Per the manufacturer’s procedures, it wasn’t acceptable to remove any pins for any component other than the one that was attached to the mobile crane, ready to be removed,” Haight said. “The likely supposition is that it helps them to get the work done faster.”