Investigators believe that a large fire that left two people dead in Surrey Monday morning was caused by electrical equipment used in a licensed medical marijuana operation.

In a news release, the City of Surrey said fire crews were dispatched to a home in the 9400-block of 163 Street at around 7 a.m.

One resident managed to escape the residence on their own and firefighters rescued another from a second-floor balcony, leaving two occupants unaccounted for.

Crews worked through the heavy smoke to pull the two residents out of the basement. Both were alive when firefighters brought them out of the home, but one of them died at the scene and the other died later in hospital, despite efforts to save their lives.

The victims have not been identified.

Neighbour Dan Kielan said he first heard sirens in the area and saw "quite heavy smoke" coming from the house when he looked outside.

"It was quite the morning. We had five fire trucks, police, ambulance—this street was pretty busy all morning," he said.

Kielan remembers crews trying to resuscitate someone for "quite some time after the fire had been burning," adding that news of the deaths was "sad and concerning."

Authorities say the fire was accidental. The residence has a valid medical marijuana licence, and a preliminary investigation suggests the blaze was caused by equipment involved in the growing process.

Kielan said he was alarmed to learn that the residence contained a grow-op.

"I feel for the people who passed away and yet, in a place where this is my home and my kids play, it's concerning for their safety and their future and I'm just not OK with this," he said.

With files from CTV Vancouver's Ben Miljure