The pilot of a chartered plane that crashed into the storage area of a shopping mall in Melbourne on Tuesday was investigated for a “near collision” in 2015, Australian officials said on Wednesday. Aviation authorities said Max Quartermain was investigated for an incident in September 2015 when his plane came within 1.8 km horizontally and 90 metres vertically of another aircraft near a ski resort in Victoria state, BBC reported.

The Australian Transport Safety Bureau had called the near-miss a “serious incident” in a summary. The report for the incident will now be published in March. Meanwhile, the Bureau said the aircraft was designed to take off with only one engine in the case of catastrophic failure, The Guardian reported. ATSB Chief Commissioner Greg Hood said Quartermain made a mayday call shortly after take off, but would say whether his aircraft had suffered a “catastrophic engine failure”.

Investigators would deliver a preliminary report on the crash in 28 days, Hood said. “The investigators are trained not to put any bias or any reliance on what is the obvious, it’s really important that when investigating an aviation transport accident that you remain completely objective,” he said. “We have discovered some interesting facets, we really need to gather all of the evidence and do the analysis before we comment.”

The twin-engine light aircraft, a Beechcraft B200 King Air, had taken off from Essendon Airport and crashed into the roof of Direct Factory Outlet shopping centre at the end of the runway at 9 am. Five people were killed. It was a charter flight headed to King Island Tasmania’s north-west coast, according to reports.

Victorian Premier Daniel Andrews had said this was the “worst single aviation accident the state had seen in 30 years”.