Residents who live near the site of derailed CN tanker train west of Edmonton are still unable to return home after a controlled burn failed to get rid of potentially explosive propane on the freight cars.

CN spokesperson Warren Chandler apologized to residents Monday morning, saying the decision was made in the "interest of safety."

A second controlled burn is being conducted in hopes of getting rid of all the flammable material inside the tankers.

"We had hoped that (a return) could take place this morning, earlier than predicted," Chandler told The Canadian Press. "That's not going to be possible and we apologize to residents."

CN said it doesn’t have a timeline for when residents can return home.

“Everybody is getting pretty tired,” evacuee Jeanette Hall told CTV Edmonton. “Everybody wants to go home.”

Thirteen cars of an 130-car CN train derailed near Gainford, Alta., around 1 a.m. Saturday morning. Four cars that were carrying crude oil remained intact, but three others carrying liquefied petroleum gas caught fire, CN said.

Approximately 100 residents are under an evacuation order after two explosions were reported. There were no injuries as a result of the derailment.

The rail company began a controlled burn of liquefied petroleum gas at the site of the derailment on Sunday. Officials said it was the safest and most effective way to allow the residents in the area to eventually return to their homes.

But Chandler said the fire exercise did not burn off all the propane in the derailed tank cars and as a result, investigators were not able to remove the freight cars.

"Unfortunately, when we went to inspect the cars… we found that not all the cars had vented their propane," he said, adding that the cars have been left to vent overnight. "(We) are now assessing the next steps."

Earlier Monday, Dan Holbrook, manager of the Transportation Safety Board's western regional operations, said team of three specialists will begin their probe of the freight train derailment once the liquefied petroleum gas has burned off.

"They will be into the site early this morning and they will be able to hopefully determine the cause of this derailment," Holbrook told CTV's Canada AM in a telephone interview.

Holbrook said train inspections, including brake tests, are conducted on a "regular basis." He said his team of inspectors will look over the train's inspection report as well as a detailed inspection report of the cars involved in the derailment.

The derailment is the third this month involving CN trains, raising new safety concerns for trains carrying flammable and explosive materials.

NDP Transport Critic Olivia Chow said more inspections are needed on both the tracks and the trains.

"Right now, it's only up to the rail companies do their own inspection. That kind of regulation is really hurting the rail system," Chow told Canada AM.

CN said no issues were found when the tracks were tested last week and train inspections were performed on Friday.

With files from The Canadian Press