TROY — The cause of the blaze that destroyed Alpha Lanes will likely remain unknown, the city fire chief said Thursday.

Chief Eric McMahon said investigators on the scene were unable to determine where the fire began in the now-demolished Fifth Avenue business.

“It’s a black hole,” McMahon said of the investigation.

The fire that began shortly before 10 a.m. Wednesday took hours to extinguish and became frightening when two firefighters were briefly trapped inside and issued a mayday. They were pulled to safety, and no one was injured.

The fire that destroyed the 82-year-old Alpha Lanes with its 18 bowling alleys also left Lansingburgh with nothing but memories of what had been a local gathering place. Demolition crews worked with firefighters into Wednesday night to clear debris and eliminate hot spots at 326 Fifth Ave.

The cause of another fire that occurred Wednesday afternoon, at a warehouse at Forest and Pawling avenues, also will likely remain unknown due to the intensity and damage, McMahon said. Firefighters did not enter that burning structure due to exploding tanks inside.

The two fires in the same day demonstrate why the city's firefighters need a second set of "turnout" gear, said Eric Wisher, president of the Troy United Firefighters Association Local 86.

The firefighters responding to both fires would have fought the second one in wet gear, Wisher said.

Firefighting gear is washed after a fire and must be hanged to air dry. Fighting a fire in wet gear exposes personnel to carcinogens that remain on the suits, Wisher said.

The Troy Fire Department has a washer to do this. To deal with the more than 30 sets of gear that needed to be cleaned, the department sent gear over to the Watervliet and Watervliet Arsenal fire departments to be washed.

It would cost the city $330,000 to outfit the entire department with a second set of turnout gear, Wisher said. He has asked the City Council to consider allocating the money. The fire department has a budgeted strength of 120 firefighters.

Council President Carmella Mantello sent a letter to the other six council members saying the topic would be discussed at the Finance Committee meeting Thursday, May 16. "It is imperative ... that they have adequate turnout gear that is free from chemicals and as clean as possible," she wrote.

John Salka, a spokesman for Mayor Patrick Madden, said the administration would take part in the discussion. He said the administration is "making investments that not only strengthen and improve the department's firefighting capacity and response capabilities, it gives the department the flexibility to continue providing important emergency services to our residents and families."