One of the Sydney siege victims may have been hit by a police bullet and not a blast from the shotgun held by Man Haron Monis, it has been revealed.

The Australian reports NSW Police Homicide Squad detectives are considering the possibility that police bullets ricocheted off the Lindt café walls, hitting the hostage, after at least one woman's injuries were found to be consistent with police fire.

Three surviving women who received gunshot wounds when heavily armed officers stormed the building shortly after 2am on December 16 were taken to different hospitals following the firefight.

They were told not to discuss the events to preserve the integrity of the "critical incident investigation".

Café manager Tori Johnson, 34, and barrister and mother-of-three Katrina Dawson, 38, were killed during the 17-hour siege's bloody conclusion, along with 50-year-old gunman Monis.

It is not clear which hostage is believed to have been hit with the police bullet.

A police officer struck in the face with shotgun pellets was also hospitalised.

It is believed that only one of the highly trained Tactical Operations Unit was designated to target Monis and that far fewer shots were fired than the dozens initially reported.

Just how many shots were fired, and by whom, is now the subject of an investigation headed up by detective inspectors Angelo Memmolo and Grant Taylor.

Post mortems have been carried out on the bodies of Johnson, Dawson and Monis.