Before members of the LAPD bomb squad destroyed part of a South L.A. neighborhood by exploding a stash of illegal fireworks last summer, they repeatedly ignored warnings from one of their most experienced technicians that the plan was not safe, according to a new report by the LAPD’s inspector general .

The member who raised concerns, identified only as “Bomb Technician C,” told investigators with the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives that he had flagged both the volume and weight of fireworks being placed into the LAPD’s “total containment vessel,” or “TCV,” as excessive and too powerful for the vessel to control all at once.

“Based on my experience and everything, I said, uh, this is too much to do one shot, we’re gonna break them up, right?” the technician recalled saying to a colleague, the Los Angeles Times reports.

He said his colleagues and his supervisor told him that he was wrong and that he should “relax,” and the fireworks were loaded into the vessel all at once anyway, the inspector general found.

“They basically told me that they had already done the calculations, that they were well under the net explosive weight that the TCV could handle,” Technician C told investigators.

The subsequent blast, on June 30, ripped open the containment vessel and destroyed much of the surrounding neighborhood, damaging nearly 40 vehicles and 35 properties, injuring 17 people (including 11 officers), and displacing dozens more residents — many of whom have never returned.

The ATF later found that the bomb squad had indeed badly miscalculated the explosive power of the fireworks placed into the containment vessel — overloading it just as Technician C had warned.