Metropolitan Transportation Authority Chairman Joe Lhota said today that construction will resume Monday at the part of the Second Avenue subway construction project that had an explosion this week, but as of now no date has been set for when blasting will resume.

MTA officials say Tuesday's explosion near East 72nd Street occurred because steel plates covering the construction site failed to withstand the impact of a controlled blast, sending rocks and debris onto the street.

Construction workers were blasting through rock to create an escalator when the two 1,800-pound steel plates were lifted into the air, raining debris onto the street.

The plates were not secured to the ground properly.

The MTA says it is putting safety first.

"What happened there was completely and totally unacceptable and from my point of view it will not happen again," said Lhota. "I won't let blasting start again. I won't put that neighborhood in jeopardy, the safety of that neighborhood in jeopardy or the safety of the workers who are there. We're building a subway on Second Avenue in some of the densest urban population in the world."

No one was injured during Tuesday's blast.

There was also no structural damage to surrounding buildings, though a vacate order was issued as a precaution for the ground floor of one building that had several windows blown out.