
A construction crane on top of an under-construction Google building in downtown Seattle has collapsed killing four people on Saturday.

The crane at the South Lake Union project collapsed on Mercer Street near Interstate 5 shortly before 3.30pm and crushed six cars below, according to the Seattle Fire Department.

Three men and one woman had died when firefighters reached the scene. It's unclear what caused the crane to collapse.

Fire Chief Harold Scoggins said two victims who died were crane operators and the other two people had been inside separate cars below.

Three people - including a mother and her baby - were also injured and taken to taken to Harborview Medical Center. Another person inside a damaged car was treated at the scene and not transported to hospital.

A spokeswoman for Harborview Medical Center, Susan Gregg, said the 25-year-old mother her four-month-old daughter suffered non life-threatening injuries. A 27-year-old man is also being evaluated for non-life-threatening injuries.

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The crane at the South Lake Union project collapsed on Mercer Street near Interstate 5 shortly before 3.30pm and crushed six cars below, according to the Seattle Fire Department

Emergency crews work the scene of a construction crane collapse near the intersection of Mercer Street and Fairview Avenue near Interstate 5 in Seattle

Emergency crews work at the scene of a construction crane collapse where four people were killed

Three people are also injured and taken to the hospital. Another person inside a damaged car was treated at the scene and not transported to hospital

The Seattle Fire Department confirmed that four people were dead when firefighters reached the scene

Emergency crews work at the scene of a construction crane collapse. Two of the vehicles crushed by the crane are seen above

Esther Nelson, a biotech research assistant who was working in a building nearby, saw the crane fall and told the Seattle Times the crane was around eight or nine stories high and broke in half

A statement issued by Seattle Fire Department said: 'Crews immediately began stabilizing the crane and vehicles involved while triaging the victims of the crash.

'Firefighters searched the building and evacuated the people in the building and impacted area.'

Esther Nelson, a biotech research assistant who was working in a building nearby, saw the crane fall and told the Seattle Times the crane was around eight or nine stories high and broke in half.

'I looked up. The wind was blowing really strong,' she said.

'Half of it was flying down sideways on the building,' she said. 'The other half fell down on the street, crossing both lanes of traffic.'

Mayor Jenny Durkan tweeted: 'My thoughts and prayers are with those killed and injured'

Mayor Jenny Durkan tweeted late Saturday: 'This is a tragic day in Seattle with this catastrophic incident in the heart of our city. My heart breaks for those who lost loved ones today.'

She earlier tweeted: 'My thoughts and prayers are with those killed and injured.'

And she later issued a statement: 'We also saw some miracles, including a mother and her young child whose car was struck by the crane but survived. We are seeing our community come together in the face of tragedy and provide comfort to each other.

'Determining how and why this tragedy happened will take time. The City of Seattle, including the Seattle Police Department, will continue to work with the Washington State Department of Labor & Industries so they can complete a thorough investigation into the causes of this incident. SDOT will also ensure any road repairs are complete.'

All eastbound and westbound lanes were closed, and motorists were told to avoid the area.

Blake Haner, a Seattle resident, holds flowers for those who died at the scene of a construction crane collapse

Workers hug at the scene after a construction crane working on a Google building collapsed in downtown Seattle

Construction workers are seen at the site above. All eastbound and westbound lanes were closed, and motorists were told to avoid the area

Firefighters arrive on the scene to assess the damage. It's unclear what caused the crane at the under-construction Google building to collapse

The crane at the South Lake Union project collapsed on Mercer Street near Interstate 5 shortly before 3.30pm

Tweets from the scene showed the crane collapsed on the street, with vehicles stopped in the vicinity

The damage caused to the under-construction building is seen above

With Amazon and other tech companies increasing their hiring in Seattle, the city has dozens of construction cranes building office towers and apartment buildings

Seattle Mayor Jenny Durkan talks to reporters near the accident site. She issued a statement which said: 'We also saw some miracles, including a mother and her young child whose car was struck by the crane but survived. We are seeing our community come together in the face of tragedy and provide comfort to each other'

According to GeekWire, Google is due to start moving into the South Lake Union neighborhood this summer.

The campus, which stretches two blocks, has been under construction for nearly two years and is due to be made up of 607,000 sq ft of office space and 149 apartments.

Google first set up a base in Seattle 15 years ago and has roughly 3,400 employees in the region.

With Amazon and other tech companies increasing their hiring in Seattle, the city has dozens of construction cranes building office towers and apartment buildings.

As of January there were about 60 construction cranes in Seattle, more than any other American city.

The road closures that will remain in place until Sunday around the accident site are seen above

A Google Maps photo above from August 2018 shows the site under construction above. The campus, which stretches two blocks, has been under construction for nearly two years