There is an internal review underway at the Public Safety Communication (PSC) Centre.
It comes after CTV News learned of a disturbing development in the case of a murdered Calgary woman.
Sources allege an emergency call made hours before her death was not properly followed up on by city operators.
Calgary's chief of police is asking for a change in policy for how the call centre handles 911 hang ups.
Yanrong Cheng was killed February 7. Police were dispatched to her home after a call to 911.
When investigators arrived, they found a woman in medical distress. She was rushed to hospital where she later died.
Her husband, 43-year-old Shengjun An is charged with first-degree murder in her death.
CTV News has learned a call was made from the victim's cell phone more than 15 hours before police were dispatched.
According to sources, the call was made to the Public Safety Communication (PSC) centre, which answers 9-1-1 calls in Calgary, at 12:41 a.m. The conversation didn't last long enough to record any voices.
Emergency operators called the victim's cell phone back right away. A man answered and a woman could be heard yelling for help in the background before the line went dead.
PSC officers called the number back twice and were eventually given an address from someone else who answered the phone.
The call was logged and a complaint attached to the address given. But it is alleged that the address given was false, and sources say PSC officers didn't check the phone number for the correct address, and no police officers were dispatched to check on the call.
Had the address been checked, sources say a previous domestic call would have come to the operator's attention.
Police were called to the home in 2009 for a verbal argument. Officers spoke to those involved and no charges were laid.
The Calgary Police Homicide Unit is aware of these latest developments.
The manager of PSC, Stephen Dongworth, says protocol was followed in this situation and after listening to the call he heard nothing that causes him to think anyone acted outside their protocols.
It is not the first time procedures at the PSC have been called into question.
In December 2009, Chief Rick Hanson called a news conference to make it clear police officers had responded immediately upon being notified about an emergency call made by a woman whose children were murdered in their home in Panorama Hills.
In that case, an earlier call had been made to the PSC but according to officials at the centre, it didn't meet the necessary criteria to be passed on to police.
Earlier last year, the Calgary Police Service also called for an independent review of the way PSC handled its emergency calls.
The chief now says if changes aren't made, he may call for a new system to be set up that includes police involvement.
Dongworth says having a trained officer on duty in the centre might make a difference but it's not necessary if the centre has the best protocols for people to follow.
PSC officials will be meeting with the police on Friday to discuss whether changes need to be made or not.
