A fire that destroyed the gatehouse at the Whitehorse landfill this morning is being treated as suspicious, says Whitehorse fire chief Clive Sparks.

Investigators from the fire department, the RCMP and the territorial fire marshall's office were on the scene as Sparks and Mayor Bev Buckway held a mid-morning press conference near the smoking rubble.

"We got a call this morning about 10 to seven from the operator of the gatehouse who arrived to find the building on fire,” Sparks said.

"The fire had been burning for quite a while before the operator arrived, which is why there is not much left.”

The chief said there are some indicators suggesting the fire was deliberately set.

Those include the fact that the locked gate along the Alaska Highway had been busted into and was open when the operator arrived.

Dave Muir, the city's manager of public works, said the landfill is closed to the general public until a new structure can be put in place.

It will remain open to commercial haulers, including contractors with construction waste to deal with, he said.

Even commercial operators are being asked to try to minimize their trips to the dump, he added.

Muir said curbside garbage collection will continue as usual.

The building was insured, though Sparks said he hasn't had time to estimate the value of damage.

Muir pointed out about $50,000 in upgrades to the building's computer system were completed over the last year, though some of that was for software the city still has.

"We are in the process right now to find another building to get the operation up and running,” said Muir.

"I believe we have a temporary gatehouse secured, and we are working on getting it in place.”

He said he expects the landfill will reopen to the public well within a week.

The operators are essential in the management of the landfill as they track the material that comes and goes through the gate, and weigh all the commercial vehicles, Muir said.

It's expected there was some damage to the weigh scales, but the extent of that is not known, Sparks said.

He he wasn't able to say this early into the investigation whether gasoline or some other type of accelerant was used.

"They are doing the investigation now and their job is to determine the cause of the fire, and once they do that, if any samples need to be tested, that will be done by the RCMP.”

But with the front gate busted open, together with the fact nobody was working and nobody should have been inside the landfill property, circumstances are definitely suspicious, said Sparks.

He said it's difficult to way how long it will take to wrap up the investigation, because it all depends on what the investigators find.

The mayor said she is concerned that this is the second major fire the city has had to deal with in under a year, and it too may have been set deliberately.

Ultimately, she said, losses not covered by insurance are carried by the taxpayers.

Buckway also encouraged anyone who may know anything to assist the investigation to come forward.

The city contracts Raven Recycling to manage the gatehouse for what was $162,000 in 2011.

The total operations and maintenance budget for the landfill last year was $1.4 million, all of which is covered by monthly garbage fees and tipping fees charged at the gatehouse.

Two girls, aged 12 and 13, have pleaded guilty to starting the June 24, 2011 fire at the Canada Games Centre, which caused more that $5 million in damage, most of which was covered by insurance.

The girls are scheduled to be sentenced later this month.