Sumwalt said there also had been a water main break at the site, but it was unknown if that contributed to the gas explosion or was caused by it. The water main was installed in 1897, the city said.
Fire and utility officials said that if the buildings were plagued in recent days or weeks by strong gas odors, as some tenants contended, they have no evidence anyone reported it before Wednesday.
The blast erupted about 15 minutes after someone from a neighboring building reported smelling gas, authorities said. Con Edison said it immediately sent workers to check out the report, but they got there too late.
Con Ed CEO John McAvoy said the call had been correctly categorized as low priority.
“A single person calling that they smelled gas outside of a building is not something that would warrant a fire department response,” he said.
Police spokesman Stephen Davis said detectives have interviewed the landlords of both buildings to help identify occupants and tenants but said none of them reported being told about gas leaks or odors.
An Associated Press analysis of the city’s 311 calls database from Jan. 1, 2013, through Tuesday also found no calls from the buildings about gas.
The lesson, De Blasio said, is that people should heed the post-Sept. 11, 2001, slogan, “If you see something, say something.”