Victoria Police have confirmed catastrophic engine failure just after take-off was behind a fatal plane crash at a Melbourne shopping centre this morning, as authorities confirm four out of the five victims were from the US.
The five - an Australian pilot and four US tourists heading to play golf on King Island - were on the plane when it appeared to suffer catastrophic engine failure moments after taking off from Essendon Airport this morning.
Although staff were preparing to open stores DFO Essendon, no one else was injured by flying debris or the fireball that engulfed the plane, burned through the stores and out into a carpark.
The Beechcraft Super King Air twin-engine aircraft struck the centre at about 9am.
The plane, owned by Myjet, had been hired by Corporate and Leisure Travel, a company owned by Max Quartermain, who is believed to have been the pilot.
CEO of Australian Corporate Jets Bas Nikolovski says Mr Quartermain is an experienced pilot.
"It has smashed me for six, and I am a softie at the best of times," he said of hearing of the accident.
The family of one of the four American golfers killed in the accident say he died on the trip of a lifetime.
Greg Reynolds De Haven and Russell Munsch have been named by their families on social media as two of the five men killed in the crash.
Mr De Haven's sister Denelle Wicht posted: "Dear friends and family, my handsome athletic big brother was killed today in a plane accident while on his 'once in a lifetime' trip to Australia.
"It was a charter flight with 2 of his friends flying to another island to play golf."
Mr Munsch was identified in a post by his cousin Carol Holst.
Victoria Police Assistant Commissioner Stephen Leane confirmed that catastrophic engine failure was behind the crash.
"Investigations are taking place and the emergency is still unfolding at Essendon fields as we speak," she said.
"The pilot has then unfortunately attempted to return to Essendon but has crashed into the DFO at Essendon fields. We've had a significant plane crash."
Police say a blaze which broke out after the crash near Essendon airfield has been extinguished.
Victorian Premier Daniel Andrews has called the crash a "desperately sad day" for the state.
He says it's the worst civil aviation accident Victoria has seen for 30 years.
"We are currently reaching out to (victims') families to provide them with the support that they need to try and comfort them at what must be such a horrible moment," he says.
"Beyond that, there are a number of people who've witnessed this terrible accident and they've been given the support, the psychological first aid that they need by Ambulance Victoria."
Premier Andrews praised the efforts of Victoria Police and the 90 firefighters who attended what he called a "complex and unpredicatble fire".
The Australian Transport Safety Bureau says it has opened an investigation into the incident involving a Super King Air aircraft and has deployed four investigators to the site.
Earlier, Superintendant Mick Frewen said the plane called in a mayday "close to taking off from the runway".
"It gained a slight degree of altitude before crashing into the back of the DFO," he said.
The DFO Essendon shopping centre was not open at the time and it remains unclear if anyone was injured inside the building when the plane impacted.
He said teams would be sent into the building - a storage area at the rear of two outlets, Focus on Furniture and JB Hi-Fi - once the fire was extinguished.
Earlier, witnesses described the scenes shortly after the accident.
"There is constant explosions going off, there is black smoke billowing into the sky," one caller told 3AW on Tuesday.
Motorists on the nearby Tullamarine freeway have posted videos and pictures of black smoke pouring out from the side of the DFO building.
Inbound lanes on the freeway remain closed, while outbound lanes have been re-opened.
Supt. Frewen says there remains some debris on the freeway and police were seeking to preserve the scene for investigation.
Police are urging commuters to avoid the area.
ABC radio caller Jason was in a taxi when he looked out the window and saw what he thought was a twin-propeller plane.
"I saw this plane coming in really low and fast. It went just behind the barriers so I couldn't see the impact but when it hit the building there was a massive fireball," he told ABC 774.
"I could feel the heat through the window of the taxi, and then a wheel, it looked like a plane wheel, bounced on the road and hit the front of the taxi as we were driving along.
"We kept driving and there was big fireball behind us."
Melbourne's Grace Martin was having a coffee when a light plane flew directly above her, crashed nearby and exploded sending her running for her life.
"My heart was in my throat," Ms Martin told reporters on Tuesday, hours after the charter twin-engine plane which was carrying five people crashed into a factory outlet store in Essendon just after take off.
"If it had been a metre lower I wouldn't be here to be honest."
Ms Martin said she saw a large hole in the wall at a nearby Spotlight store with water pouring through it.
She said the plane was on an angle when it flew over her and it looked like it only cleared the building by a metre.
"It flew over the top of me and it was shaking on the way down and a metre from the top of the roof," Ms Martin said.
"That's when I ran away and heard the big crash and saw all the flames."
Ash Mayer, a storeman at The Good Guys, felt the crash reverberate through his building.
"We were just coming off the off-ramp, we felt just everything shake and a massive explosion and a fireball go up," he told AAP.
"We just knew this was bad and there was nothing we could do.
"One of the boys actually saw it go down and he's now left because he can't deal with it."
Witness Carmel Brown told AAP there was a huge explosion when the plane hit.
"There was a big crash and then a big red fireball, like a mushroom," she said.