Ten months after a downtown fire destroyed seven businesses one block south of the New Haven Green, city officials still do not know the cause of the three-alarm blaze.

Fire investigator Capt. John Coles released a 90-page report last week detailing the 911 calls received by the emergency dispatchers, firefighter accounts of extinguishing the fire, and a damage summary, but the report stated that “the cause of fire is undetermined at this time due to the hazardous conditions within the Brass Monkey night club.”

The Brass Monkey at 29 Center St., the bar where the Dec. 12 fire is believed to have started, was demolished five days after the fire because of structural damage to the building. Coles explained that investigators had little time to examine the building before it was sealed off and torn down.

Ward 7 Alderwoman Frances “Bitsie” Clark said it was “disappointing” not to learn the cause of the fire, but she said that not knowing the cause could have even greater repercussions for the city. Paul Denz, a landlord of most of the buildings in the area, filed a lawsuit against the city for tearing down his property prematurely.

The owners of the Brass Monkey Lounge told Deputy Fire Marshal Frank DellaMura that they invested a significant amount of money in the club, which opened less than a month before the fire. Although the cause of the fire is still unknown, NHFD officials have not suggested the club owners are at fault.

Fire officials have yet to determine whether the building’s sprinkler system was activated once the fire began. Three months before the fire, Brass Monkey nightclub owner Mark McKinley accidentally struck one of the sprinkler heads on the ceiling of his club while performing renovations. At that time, the sprinkler system was activated, water poured from the ceiling and the audible fire alarm sounded.

But on the night of the downtown fire, no one reported hearing the audible alarm. Because of the volume of water used to extinguish the Brass Monkey fire, it was impossible to tell if water was discharged before fire fighters arrived on the scene, DellaMura said in the report.

The control for the sprinkler system was recovered in the fire debris and was switched to “on,” and the shut-off valve for the sprinkler system was still padlocked when the fire was extinguished.

Coles explained in his report that the fire most likely began in the “cock loft area” of the Brass Monkey nightclub, a three- to four-foot area above the Brass Monkey ceiling that also stretched out above the ceilings of the Madrag and Expressions nightclubs.

Fire trucks responded to the fire four minutes and 35 seconds after the emergency dispatchers received the first 911 call at 6:35 a.m. the morning of the fire. Residents living close to the fire reported seeing flames and black smoke escaping the Brass Monkey, Madrag and Expressions. The first 911 caller was a 15-year-old male who was walking to a nearby bus stop on his way to school when he spotted smoke and called the fire department.

An emergency dispatcher advised one of the 911 callers to exit the building in which the person was making the call. Several residents continued to call 911 even after the fire department arrived, advising fire trucks to go around a different side of the building where flames had begun to peek out of the structure.

Along with the complete destruction of the Brass Monkey, the downtown fire — which cost the city $10 million in damages and lost revenue — also resulted in the demolition of Expressions nightclub, Madrag nightclub, the China Town Beauty Supply Store, New Haven Furniture and Linen, the Concord 9 Jewelry Store and sections of the New Haven Variety Store.