The lights will soon be back on for 5,000 residents in Calgary after a four-day blackout in the city’s downtown core.

According to city officials, residents can return home -- and employees can get back to work -- as early as Thursday morning after an underground fire over the weekend wiped out power to a number of downtown buildings. 

Calgary utility Enmax has had repair crews working around the clock to return power following the Saturday evening incident. Early estimates suggested the power would be out for at least four days, but as long as a week.

Calgary Mayor Naheed Nenshi broke the welcome news in a press conference on Wednesday.

“Enmax now believes they are in a position to re-energize the entire affected area tomorrow at 5 a.m.,” he said 

Officials caution that people shouldn’t expect to get into their buildings right at 5a.m., as building managers and city inspectorswill have to make sure ventilations systems, water, elevators and heating are all working first. 

"This has been a major rebuild, so we may encounter some issues," said Enmax President and CEO Gianna Manes.

While the power may return sooner than expected, the news is too little, too late for some residentsand businesses. According to the Calgary Chamber of Commerce, there are more than 1,000 businesses and 10,000 employees in the downtown core. 

Bakery manager Sunny Cho estimates that the blackout has cost her business $20,000.

“All the customer orders has been cancelled; a lot of customers are so mad about that,” she told CTV Calgary.

Restaurant owner Douglas Hernandez, of Jalapeno’s Mexican Grill, told CTV Calgary that the power outage has cost his restaurant more than $5,000 in lost business and spoiled food.

When businesses and residents do return, they are being asked to throw out rotten food immediately. The city will be providing additional Dumpsters for the spoiled food, picking it up until 7 p.m. Thursday night. 

Building owners will need to be on location for re-energization and employers will need approval from the proper authorities before going back to work, according to a statement from the Calgary Chamber of Commerce. 

A full breakdown on what Calgarians can expect from the powering up process can be found at on the Calgary Chamber of Commerce’s website.