Bad construction is allegedly to blame for a six-alarm fire at a Dorchester condo building last month.

An improperly installed exhaust pipe was heated by diesel fumes that sparked wood framing on the top floors of the $45M Treadmark building, the Boston Globe reports. The June 28 fire engulfed the multifamily development just as it was undergoing an emergency system test. The situation worsened after construction workers waited an hour to call firefighters, Boston Fire Commissioner Joseph Finn said at a press conference Wednesday.

Trinity Financial is developing the 83-unit complex, which includes both market-rate condos and affordable apartments. A cast-iron exhaust pipe ran from a basement emergency generator through the six-story building to the roof. Architectural plans called for a 12-inch clearance around the pipe, but it was installed with just three inches of space around it.

"The circumstances of the Treadmark fire are still under investigation by many parties; therefore, we must reserve any comments until the investigations are complete and the official reports are released," Trinity spokesperson Susan Elsbree said in a statement.

The Dorchester fire has drawn further attention to a series of fires at wood-frame apartment construction sites around the country.

A 10-alarm fire broke out Sunday at the 264-unit Edison on the Charles apartment complex under construction in Waltham. A five-alarm fire in April at a 275-unit apartment complex under construction in suburban Washington, D.C., caused $39M in damages. Despite the fire risk, rising construction costs have kept wood as a popular choice with developers.