Here's what we know — and don't — about the $20M heist at Pearson airport

The theft of gold and other pricey items worth an estimated $20 million from a container at Toronto's Pearson International Airport continued to be the subject of an intensive police investigation Friday.

In a statement to CBC News, the Greater Toronto Airports Authority (GTAA), which runs the airport, said thieves accessed the public side of a warehouse leased to a third party and that the area is outside of its primary security line.

The high-stakes heist has drawn international attention, with many asking how such a brazen robbery is possible.

With police tightlipped about their investigation, there are still many unanswered questions. Here's a breakdown of what we know, and what we don't, about what happened at Pearson.

The container arrived Monday: Insp. Stephen Duivesteyn, spokesperson for Peel Regional Police, told reporters Thursday that the container arrived on a plane early Monday evening. The plane was unloaded according to normal procedure and its cargo taken to an airport holding facility before it was "removed by illegal means."

When police learned about the theft: According to Duivesteyn, the theft was reported shortly after it was discovered.

There are no ongoing threats to passengers or GTAA staff: The GTAA says the theft did not involve access to Toronto Pearson itself and did not pose a threat to passengers or GTAA staff. In fact, Duivesteyn said investigators believe "this to be an isolated incident." He said travellers who may be concerned about going through Pearson should have no concerns. "We do not consider this to be a public safety matter."

There were no disruptions to airport operations: Pearson airport remains open and there were no disruptions to airport operations.

No arrests have been made: As of Friday, no one has been arrested in connection with the heist and no possible suspects have been publicly identified by police.

There are many open questions about the robbery. Here are some key facts that remain unknown at this time:

WATCH | What police will be looking for in the investigation:

Former RCMP deputy commissioner Pierre-Yves Bourduas says there was obviously a "break in protocol" at the airport, because when these types of cargo arrive at an international port, there are strict guidelines to follow to ensure their security.

Bourduas told CBC News he found it to be "quite surprising that you have a container that was breached and $20 million has essentially vanished."

He expects the investigation will try to determine the following: