Seventy-seven years have passed since a fire ripped through the Cocoanut Grove nightclub in Boston, killing 492 people. To this day, investigators are still trying to figure out how the flames spread so fast through the building.

“The official cause of this fire is unknown,’’ said Casey Grant, executive director emeritus of the Fire Protection Research Foundation. “The big mystery is why did it spread so rapidly? Why did this fire burn so rapidly, so violently in such a short amount of time?’’

Earlier this month, Grant gave a talk to the Boston Sparks Association and presented the latest research and insights about this fast-moving fire that killed so many people on Nov. 28, 1942. Grant also appears in a new video about the Cocoanut Grove fire on the National Fire Protection Association’s YouTube channel.

“This was a very fast fire,’’ he said.

Grant created diagrams that illustrate the flow of the fire and how it moved though the building. He also put together a detailed, minute-by-minute timeline of what took place on that fateful night.

It was a Saturday night, and Boston College’s football team had just lost in a stunning upset to Holy Cross at Fenway Park. (But it probably saved their lives; Boston College ended up canceling its post-game party at the Grove.)

The fire was first seen around 10:15 p.m. in the Melody Lounge, which was located in the basement of the club. The room was decorated with artificial palm trees, and the ceiling was covered by a blue satin-like fabric.

The first flames were seen burning in a palm tree and the suspended cloth ceiling in one corner of the lounge.

Moments before that, a busboy had reached into the palm tree to screw in a light bulb, and he lit a match so he could see in the dark and locate the socket.

Initial reports that the busboy accidentally started the fire with the match were never substantiated, and in 1943 state Fire Marshal Stephen C. Garrity cleared the busboy of blame, stating, “It is clear to me that he did not ignite the palm tree in the Melody Lounge.’’

It’s possible that the act of screwing in the light bulb sparked the fire, Grant said.

“The place was full of unlicensed shoddy electrical wiring,’’ Grant said. “The substandard electrical wiring was very suspect.’’

The fire flashed across the cloth ceiling. The burst of flames shot across the room and rushed up the stairwell. Witnesses in the lobby on the ground floor described a “ball of fire’’ and bluish and yellow flames traveling just below the ceiling. A number of people’s hair caught on fire, and their heads were burned. The fire shot across the foyer and continued to race overhead through the main dining room and into Broadway Lounge.

In the video, Grant explained that the concave shape of the foyer ceiling propelled the fireball “almost like it was shot out of a gun.’’

In less than five minutes, the fire that started downstairs in the Melody Lounge had reached the other end of the building.

What was also strange was what didn’t burn. There were plenty of combustible materials that were untouched by the fast-moving fire.

Boston Fire Commissioner William Arthur Reilly noted this in his 1943 report on the fire:

“Much of the cloth, rattan and bamboo contained in the Melody Lounge, and on the sides and lower walls of the stairway leading therefrom, was, in fact, not burned at all, and the same is true of the carpet on the stairway, contrary to all usual fire experience,’’ he wrote.

Grant has also analyzed the medical injury data closely. He examined where patrons were when the fire broke out, and what kinds of injuries they sustained. Grouping patrons together by location and studying their injuries that way provides more insight into the behavior of the fire.

Out of the 1,000 people in the Cocoanut Grove that night, 492 died. The main entrance was a revolving door that ended up getting jammed. Other exits were locked. “Every way in and out [of the building] had something functionally wrong with it,’’ he said.

Only one out of four people escaped unharmed.

The mix of injuries that people sustained was unusual, Grant said. Some people were found dead in their chairs — they had hardly been burned, but they succumbed to the poisonous gas that was given off by the fire. Other people sustained burns but had little respiratory damage.

To this day, it’s not clear what exactly contributed to the rapid spread of the fire, and the toxic gas it produced has not been identified, Grant said.

“It should never have spread the way it did,’’ he said.

It’s possible that a flammable refrigerant was involved, and the interior finish may have somehow contributed to the blaze.

“It was a flash fire that swept through this place with remarkable speed,’’ he said. “This was a really, really fast fire. and mysterious in that sense. We still don’t have an understanding of what happened there.’’

“It is still an unsolved mystery,’’ he said.

Emily Sweeney can be reached at esweeney@globe.com. Follow her on Twitter @emilysweeney.