The owner of the Spanish Christian Church in East Harlem, New York City, which collapsed after a large explosion, told local media she smelled natural gas the night before the blast.

Law enforcement officials have ruled out a terrorist attack and told CNN that the building collapse was caused by a gas explosion.

Other reports say that an NYC utility company, Consolidated Edison or ConEd, was called to the Harlem building before the explosion due to a possible gas leak.

Neighbours reported of smell of gas before the collapse.

Carmen Vargas-Rosa, who owns the church, said there was a gas smell at the church on Tuesday night, adding that four of her tenants were unaccounted for.

"One of them was off from work so most likely she was in the building," Vargas-Rosa told CBS.

"We have a mother who has a sick son, so unless they were at an appointment in the hospital, they may have been in the explosion and then we have a young man and his wife who go to school late so they may have been sleeping and we can't reach them."

The Spanish Church owns a six-storey apartment building in 1644-1646 Park Avenue, east Harlem. A pile of debris could be seen where the building once stood with thick grey smoke rising from the area.

Authorities were responding to reports of people trapped in the rubble.

NBC News is reporting at least four people have been transported to area hospitals. Other reports say that 16 people were injured in the explosion, of which 12 have minor injuries.

The NYC fire department confirmed that a "multiple dwelling explosion and collapse" occurred in East Harlem.