Just this May, the Fire Department of New York posted training materials on its internal website detailing some of the difficulties encountered while battling blazes in homes brimming with hoarded belongings: blocked entryways, deep-seated fires and debris piled so high that, in smoke conditions, a “firefighter crawling atop can accidentally crawl out a window.”

The locations, known as Collyers’ mansions after the two brothers who died in their overstuffed home in 1947, present such dangers to firefighters that the department tries to keep track of them. As local fire companies become aware of hoarding conditions, a note is appended to the address in the Fire Department’s internal dispatching system so that arriving firefighters can be aware of what to expect.

The cluttered 19th-floor apartment where Lt. Gordon Matthew Ambelas died on Saturday night had not been identified as a Collyers’ mansion, fire officials said.

The department was still piecing together the circumstances surrounding his death, which the city medical examiner said Monday had been caused by a combination of smoke inhalation and burns. Investigators quickly homed in on the apartment’s crammed interior as a possible contributing factor, describing the home as presenting “Collyers’ conditions” in the hours after the fire.