Investigators from the D.C. Fire Department, Metropolitan Police Department and federal Alcohol, Tobacco, Firearms and Explosives are probing the gutted shell of a Capitol Hill landmark to determine what started a four-alarm fire at Frager’s Hardware that sent clouds of black smoke into the air in D.C. June 5.

Scores of firefighters worked for hours to extinguish the blaze, which erupted about 6:30 p.m. The store, located at the corner of Pennsylvania Avenue and 11th St., SE, has been a fixture in the neighborhood since 1920.

Spectators looked on in awe and sadness as the fire consumed the building. More than 200 firefighters worked to extinguish the fire. At one point, police pushed viewers back from the fire scene, fearful that propane tanks stored inside the store might explode as the fire spread through the building.

In addition to propane tanks, the venerable shop where rare hardware was available had larged stores of helium and highly combustible gardening products jammed into a space with narrow aisles.

Residents watching the disaster compared the blaze to the fire at Eastern Market on April 30, 2007. That fire badly damaged the market, which was closed for some time and later restored.

Two firefighters suffered minor injuries in the fire, a fire department spokesman said.