CN officials at the scene of a fiery train derailment west of Edmonton have carried out a third controlled burn, but more than 100 people living near the derailment are spending a third day away from their homes as railway officials say it's not yet safe enough for them to go back.

"We had hoped [the return] could take place this morning, earlier than had been predicted," said spokesman Warren Chandler. "That's not going to be possible and we apologize to residents."

Thirteen cars carrying oil and liquefied petroleum gas went off the rails near Gainford, about 80 kilometres west of Edmonton early Saturday.

An earlier attempt to use explosives to punch more holes into two ruptured train cars containing liquefied petroleum gas (propane) Sunday night to help burn off the gas did not work.

"We had hoped the exercise would burn off all the propane in the cars so that we could move in, remove the cars and allow people to go home," Chandler said.

"Unfortunately, when we went to inspect the cars at 11 p.m. last evening, we found not all the cars had vented their propane. In the interest of safety we withdrew," Chandler said.

After a second burn on five tank cars, official found that liquefied petroleum gas remained in one last car, prompting them to perform another burn. 

The entire area remains under a local state of emergency while CN and Transportation Safety Board officials work to extinguish the flames.

No timeline for residents to return home

It's not yet known when the 126 residents registered as evacuees can return home.

"We will not speculate at this time how long it will take to return them to their homes," said Parkland County spokeswoman Jackie Ostashek.

CN, Alberta and Parkland County officials update media

Residents displaced by a train derailment received bad news from CN, Alberta and Parkland County officials at a media briefing Monday. They still do not know when they can return home. (Trevor Wilson/CBC News)

She warned residents against sneaking back to their homes.

"Residents returning to the scene without proper authority can cause unnecessary delays and further risk to themselves and to emergency personnel," she said.

Chandler said it was too early to estimate the cost of the crash, cleanup or property damage, though CN will compensate residents.

CN has begun looking into the cause of the derailment, but it's not known when more answers will
be available, Chandler said.

CN has said the 134-car train was travelling to Vancouver from Edmonton at a normal speed of 35 km/h when it derailed.

VIA Rail passengers bused to Edmonton

VIA Rail passengers had to be bused to Edmonton Saturday night from Jasper following the derailment.

The 88 passengers travelling from Vancouver east stayed in Jasper overnight before being taken to Edmonton and flown to their final destination from there, said spokeswoman Mylène Bélanger.

On Saturday night, an eastbound train from Vancouver to Toronto arrived in Jasper at 5:30 pm MT with 88 passengers.

The next VIA train that may be affected is due to arrive in Edmonton 6:22 a.m. MT Tuesday with 108 passengers on board.

Those passengers are waiting to find out from CN whether the train will be able to get through.

Affected customers will get a refund for part of their trip and a "late-train credit," a discount on their next trip, Bélanger said.

The Yellowhead Highway — the main east-west corridor in northern Alberta, connecting Edmonton with Jasper — remains closed Monday.