An overnight fire has caused significant damage to the Wits End Pub and Grill in London's north end.

Emergency crews were called to the restaurant on North Centre Road, northeast of Richmond Street and Fanshawe Park Road around 3 a.m., but the fire had already caused damage to the kitchen and dining room areas.

Ryan Dick, an inspector with the London Fire Department, says "Crews entered through the front entrance...worked their way through the northwest corner of the building. The fire appeared to be mostly extinguished by that point but there was heavy heat."

Emotional owner Said Chahine says "We are a family here. Like, I know most of my staff and their families...some of them I knew them when they were patrons here."

The pub employs about 20 people, including several members of Chahine's family, and he says "My goal is to open it as fast as I can, but we will see how this is going to work out."

Fire crews were able to contain the fire to the pub, leaving the rest of the three-storey office building undamaged, though employees were sent home until the air quality could be tested.

Officials are calling the damage "extensive" and the investigation continues.

While no confirmation of the cause of the blaze has been released, early indications are that it is not suspicious.