Eyewitness News has learned that the investigation is now clearly-focused on human error.
Specifically, how the explosives were placed and angled, and why steel blast cover plates were not fully-secured when the explosive charge was set-off.
"It had all of the force directed in one particular area, that was not anticipated," said Adam Lisberg, MTA Chief Spokesman.
The MTA's chief spokesman told Eyewitness News the explosion was concentrated in one area, and for that reason, workers and supervisors failed to anticipate the force of the blast. And the blast cover was inadequate to contain it.
"When you put the explosives at an angle the pressure goes upwards, so instead of moving laterally it will shoot the rock upwards, the cover was supposed to absorb all of the pressure and it did not," said Michael Horodniceanu, MTA Capital Construction.
The explosion sent a geyser of debris eight stories into the air at 12:45 in the afternoon on Tuesday and left a carpet of rubble across 72nd Street. No one was injured, because the street had been cleared before the blast.
"It was an accident waiting to happen and they were very fortunate that no one was hurt, I don't think they know how fortunate they were," said Carole Cusa, a neighbor.
Tuesday's demolition was intended to make-way for an underground escalator to the new 72nd Street subway station, and aimed at a 35 degree angle.
Some residents say the mishap is proof that the MTA and its subcontractors are not doing enough to protect them.
"I would not say it is typical that we have debris flying everywhere, but it's typical that we have explosions, that's an unfortunate set of circumstances, but it's unfortunate that it's a disruption to our lives," said Laurie Zeppieri, a neighbor.
WAKE UP WITH EYEWITNESS NEWS! Click here to download the WABC Eyewitness News Alarm Clock app from iTunes. or search WABC or 7online in the app store.
Get Eyewitness News Delivered