First three people - one staff member and two others – were seen running out from inside the cafe on footage shown on Channel 7.
Later, two women workers of the cafe were also seen running out.
According to New South Wales Deputy Commissioner Catherine Burn, the people who came out of Lindt Cafe at Martin Place were with police.
"The information that I have is that nobody has been harmed or injured at the moment," she said.
"We clearly are dealing with a situation that is unfolding and it's happening as we speak and the most important thing is the safety of those hostages and I wouldn't want to do anything that may impact on the safety of those hostages."
Burn said she could not confirm the number of people remaining inside the cafe.
"Those operational details will be forthcoming but its not a good time to speculate."
"Police negotiators have had contact and they will continue to have contact," she said.
"A peaceful resolution will be what we are working for," she said.
The siege incident came hours after a Sydney man was arrested in a counter-terrorism raid but the Commissioner said the two didn't appear to be connected.
As a security precaution, the US Consulate General in Sydney has been evacuated, along with other buildings in the vicinity of Martin Place.