BOARDMAN — Four members of a work crew in the Realty Tower building’s basement and vault area who were clearing antiquated and outdated pipes and other infrastructure and debris had no idea any gas was in one of the lines, a National Transportation Safety Board member said.

“The crew was unaware that one of the pipes in the vault was pressurized at the time, nor did the work crew have reason to believe gas was present in the pipe,” Thomas Chapman said at the NTSB’s second news conference Friday evening at the Holiday Inn in Boardman, regarding the natural gas explosion that took place shortly before 3 p.m. Tuesday at the 12-story structure.

“No gas was smelled during the day as the crew was working in the basement. This indicates that there was no ongoing leak throughout the day. The accident sequence began as the crew made two initial cuts into piping along the basement wall. When a third cut was made, the crew immediately realized there was a problem and gas was released.”

Friday also marked the first full day of the agency’s investigation into the blast that killed Akil Drake, 27, a Chase Bank employee, and injured seven others, including one critically.

As soon as the workers realized such a problem existed, they alerted employees at Chase Bank on the building’s first floor and pulled a fire alarm, and at least one of the workers called 911, Chapman said. Workers also made immediate efforts to alert and help evacuate residents as quickly as possible, he added.

The NTSB also has obtained security video from inside Chase Bank, along with video from other sources, and will examine it as part of the investigation, he said. The footage was stored in a cloud-based system Chase Bank had set up, he added.

At Friday’s news conference, Chapman was unable to speculate about why pressurized gas was in the out-of-service line that had been cut three times, except to say that the explosion occurred about six minutes after the third cut.

A crux of the investigation is determining if third-party work to clear the basement of the old infrastructure could have led to the blast.

Chapman said he was unsure whether Chase employees heard the initial fire alarm, but that they were alerted about impending danger. Also, the blast was an accident, with no evidence of nefarious activity, he added.

It remains unknown if the building is structurally sound, given the amount of damage to it.

“Regarding the building, there are very serious concerns about the integrity and the safety of the structure. Consequently, access is not currently possible by us nor by anyone until appropriate determinations are made regarding its safety,” Chapman said, adding that such a determination is in the hands of city, county and state authorities.

Chapman stressed that the NTSB’s latest information is preliminary, as its investigation is in the early stages. A full preliminary report should be available in 30 days, and the NTSB team will be on scene for about a week.

Documentation obtained Thursday by The Vindicator shows the Youngstown Board of Control on April 25 approved paying $140,133 to GreenHeart, a Boardman-based property development and management company, to remove the utility lines — water, gas, electrical, data and phone lines, sprinkler lines and furnace water tanks — from under the sidewalk in front of Realty and relocate them to its basement.

On Friday, Youngstown Mayor Jamael Tito Brown released a statement regarding GreenHeart.

“The city contracted with GreenHeart to perform private utility relocation in the basement of the Realty Tower and prepare it for infilling as part of the SMART 2 project. As per normal practice, the contractors commenced work on their own schedule, means and methods. At this time, there is no evidence to suggest the gas line mentioned in the May 30 NTSB briefing was necessary to fulfill this scope. The NTSB investigation to understand the work being done at the building at the time of the leak and explosion is still ongoing.

“Our focus remains ensuring the safety and security of the public and the well-being of those displaced by this incident. We will continue to provide regular updates through our official channels as they become available. We ask for continued condolences for the family of Akil Drake, the Chase employees and those impacted by this tragic event.”