LaSalle Heights had been built to solve a problem. In 1955, LaSalle Heights Inc. announced a $5.3-million development at the corner of rue Bergevin and rue Jean Milot -- 25 identical U-shaped buildings, each housing 36 units, totaling 678 apartments for low-income families on the Island of Montreal. Rents ranged from $30 to $57 a month, available only to families whose income was four to six times their monthly payment. The development offered three-bedroom row houses, two- and three-bedroom apartments, and bachelor units. For hundreds of working-class families, LaSalle Heights represented something rare in 1950s Montreal: decent housing they could actually afford. The buildings were plain, practical, and absolutely uniform. Every block looked the same. Every cellar ran the same gas lines.

The fissure opened in the natural gas supply line beneath 367 rue Bergevin. The explosion that followed did not merely damage the building -- it erased it. Where a three-story apartment block had stood, a crater gaped in the frozen ground. The blast destroyed units across four consecutive addresses: 361, 363, 365, and 367 rue Bergevin. Approximately 36 apartments were obliterated. By 8:25 -- just twenty minutes after the explosion -- the LaSalle fire department had arrived, joined by naval officers from a nearby barracks who raced to the scene. Rescue workers pulled survivors from rubble still clouded with gas and dust. The dead were found in kitchens, bedrooms, and stairwells, many of them still in nightclothes. Coroner Marcel Trahan began releasing names by 10 that evening. A fuller list followed two days later. Four people were still missing.

The casualty list reads like a neighborhood registry. At 365 rue Bergevin, the McGuigan family lost a mother and three children. Vera Peard, 39, died alongside three of her four children -- Kevin, Dianne, and Sharon. Mary Czopko and her daughters Brenda and Johanne were killed; Mary was initially declared dead on the day of the blast, but she had survived with a broken back, only to die on March 26. James Dyer, a 35-year-old roomer with the Czopko family, also perished. At 367, the three Rehanek sisters -- Donna, Vera, and Anne-Marie, ages eight, five, and two -- were gone. Emma Arsineau, 50, and her three-year-old granddaughter Sandra Dawson died at separate addresses. Three-month-old Marc Anthony Fernando. One-year-old Sheila Jones. Three sisters named Sylvia -- Gail, 16; Heather, 10; and Donna, 4. Of the 28 dead, the majority were women and children who had been home on a Monday morning.

By afternoon, Quebec Premier Jean Lesage and multiple deputies and ministers had arrived to survey the devastation. A relief foundation was created within days. A radio and television telethon raised approximately $600,000 for the victims and displaced families. Queen Elizabeth II sent a personal message of condolence: "I am most deeply distressed to learn of the tragic accident which has taken place in Ville LaSalle. Please convey my sincere sympathy to the mayor, to the injured, and the next-of-kin of those who have lost their lives." The Central Mortgage and Housing Corporation made roughly 60 vacant homes available to the more than 200 residents left homeless, with rent waived for two months. On March 29, LaSalle Heights Inc. announced that any tenant in the development could break their lease without penalty.

The investigation that followed pointed to a single, devastating cause. Metallurgists Andre Hone and William Williams concluded that a cracked pipe -- most likely damaged during transportation or installation a decade earlier -- had allowed natural gas to accumulate in the cellar until ignition became inevitable. The infrastructure that was supposed to serve these families had been flawed from the start. In November 1965, Herbert Peard -- who lost his wife of 15 years and three of his four children -- filed an $85,000 lawsuit against Quebec Natural Gas Corporation, including $21,000 on behalf of his surviving daughter Susan, who had suffered multiple fractures in the blast. In February 1967, LaSalle Heights Inc. itself sued the gas company for $853,275. Today, a public square at Boulevard LaSalle and Rue Lyette bears the name Place du 1er-Mars-1965. A commemorative stela stands there as a memorial -- not only to the 28 who died that morning, but also to victims of an earlier explosion in the same neighborhood on August 28, 1956. The stone reminds passersby that beneath the ordinary surface of a residential street, invisible systems carry invisible risks.