Bob Leek, a Toronto Fire Services district chief who died on the job Sunday while surveying damage from a massive propane explosion, is being remembered as a warm and giving man who always found time to help young recruits.

"He could have easily given his tasks in the field to another individual. Instead Bob chose to aid in field operations. He died doing what he loved so much, helping other people," said Ryan LeBlanc, an EMS dispatcher who trained at the fire academy under Leek.

LeBlanc sent an email to CTV.ca after he learned his friend and mentor had died while attending the scene of a six-alarm blaze which broke out at a propane facility in north Toronto. While the official cause of death has yet to be determined, it appears the 55-year-old's death was not the result of a work-related injury.

"When I was no longer under Bob's command, as a student, his door remained wide open to me," LeBlanc said. "There was one instance where I sought out Bob's guidance. Without hesitation he glanced at his schedule and invited me to his office. He was busy learning the ropes of a new assignment, having recently been promoted, yet he deliberately set aside time for me so we could chat.

"Bob was always a selfless man who did whatever he could to help people," he continued. "Bob's passion for helping others was only rivalled by his knowledge and expertise. The combination of the two set him apart, not only in the fire service but among professionals."

Leek was with the service for 25 years, fire officials said Sunday.

"Every effort was made to resuscitate him. However we do regret to inform everyone that we did lose one of our members today," Division Chief David Sheen told reporters late Sunday.

"It was not a traumatic injury; he wasn't impacted by anything. It was just in the course of him performing some operations that he went down," said Sheen, who personally knew Leek.

"It's hard," he added, fighting back tears. "I'm sure that all of our guys are having a rough time with it."

Toronto Mayor David Miller had earlier said his "thoughts and prayers" were with the firefighter's family.

Funeral and memorial arrangements have not been publicly announced yet.

The Fire Marshal's Office is investigating the blaze which resulted in more than 12,000 people being forced to evacuate an area around Keele Street and Wilson Avenue.

An employee of the Sunrise Propane Industrial Gases facility is still unaccounted for, police said.

Several people were injured in the blast but they all suffered non life-threatening injuries.