MTA officials believe the angle of a blast at the site of Second Avenue subway construction Tuesday may be to blame for the smoke and debris that covered parts of the avenue aboveground.
Though they are still looking into the official cause, the agency said the blast points of the rock were drilled diagonally when they should be drilled vertically.
The angle of the rock and the drill points caused the blast to move upwards.
The steel deck above it was not strong enough to sustain the explosion, allowing rock and other material to fly into the air.
In the meantime, the MTA ordered work at the 72nd Street site to stop.
Blasting won't continue until managers submit a new operating procedure for explosives.
"We expect that they will produce for us a new standard operating procedure for blasting," said Michael Horodniceanu, the president of MTA Capital Construction. "When we are convinced that all of these things are in place, then we will release them to work."
In order to ensure a similar incident doesn't happen again, the MTA said they are adding heavy protective mats around the blast site.
They will also hire an independent safety contractor and use more blasting consultants at each site.
The decking system will also be reviewed and there will be an increase in areas off limits to pedestrians.
The MTA said the added consultants will not increase the overall cost of the project and the added safety measures will not increase the amount of time it takes to get the project completed.
Residents remained frustrated with the MTA on Wednesday.
"It seems a little shocking that they didn't plan for that at all," said one. "I mean, it doesn't seem like they planned for proper construction."
Horodniceanu expressed frustration of his own Wednesday.
"I'm really upset and angry that we have, that whatever happened put the residents in area in the situation that it was," he said.
The first phase of construction for the Second Avenue line is expected to be up and running by December 2016. That phase is from 63rd Street to 96th Street.