Sources revealed that the two privates were not rostered to work on December 29, last year — the night the Lance Corporal died — and it remained unclear clear why they turned up for duty that night.
Additionally, investigators have learnt the night Cpl Marshall died, he too was not rostered to work, since the roster in the hands of the police indicated he was supposed to work on the night of December 28.
Police are trying to ascertain who changed the roster, or if the late Lance Corporal was given instructions to show up for duty on December 29 and who gave those instructions.
Yesterday, the team of investigators were working feverishly to have the two privates interviewed.
A senior officer of the TT Defence Force is also expected to be quizzed.
Up until yesterday, officers probing the death of the late soldier were treating his death as a homicide.
Senior police officers told Newsday they were yet to receive any of the autopsy reports from Government forensic pathologists Dr Eastlyn McDonald-Burris, Dr Valery Alexandrov, and Professor of Pathology Dr Hubert Daisley.
Newsday understands the police are expected to receive those reports by the end of this week.
The first autopsy report by pathologists Dr Burris and Alexandrov revealed the Lance Corporal died from strangulation, while the second autopsy by Dr Daisley revealed that his findings were consistent with the first.
However, Dr Daisley later told relatives he was wrong in his prognosis and the Lance Corporal may have died from asthma.
On December 29, the Lance Corporal was found unconscious next to the clothing and equipment container at the Defence Force Headquarters in Chaguaramas.
He was rushed by army medics to the Seventh Day Adventist Hospital in Cocorite where he was pronounced dead.
Relatives of the dead soldier continue to insist he was murdered, although the Lance Corporal had a medical history of asthma.
However, tests carried out on the lungs of the soldier last week by Dr Alexandrov revealed there were no signs of asthma complications at the time of his death.
Yesterday, Deputy Police Commissioner Mervyn Richard-son said the police were working round the clock to bring closure to the investigation.