McGrath claimed that if the accused are found guilty, they must be punished for their racist behavior towards the 26-year-old fast bowler.
Play was stopped for about eight minutes on day four when Siraj complained to on-field umpires about racist chants from a particular section of the SCG crowd.
About five to six spectators were asked to leave the ground and only then was the match resumed.
Speaking to Sony Six, Glenn McGrath stated that Cricket Australia, with the help of the New South Wales police, must find out what exactly happened and gather evidence to punish the accused.
"If there were racist comments, they should be prosecuted because there is no room for that. They should get those guys and find out what happened and interview the people around," Glenn McGrath said.
Racist chants to Mohammed Siraj looks bad on all Australians: Glenn McGrath
This was reportedly not the first time Mohammed Siraj received racist abuse in the third Test. He also faced similar chants from the SCG crowd on day three, which forced India to lodge a complaint to the match referee.
Glenn McGrath believes that the alleged racist remarks made on Mohammed Siraj do not keep the Australian culture in good stead. He feels it has tarnished their reputation and is something that should be dealt with strictly.
"That looks bad not only for Cricket Australia, SGG trust but all Australians and that's not how we are as a culture. That's not the way we want to be viewed from other countries," Glenn McGrath asserted.
Some of India's former cricketers and cricketing experts have also used strong words against racism faced by Mohammed Siraj, and hope that he gets justice.
Coming back to the game, Australia have set Team India a target of 407 runs. The visitors have ended day four on 98-2.
With both Ajinkya Rahane and Cheteshwar Pujara at the crease, Team India will be hopeful of a rearguard action on day five to help them save the SCG Test.