NEW YORK (CBSNewYork/AP) — Heartbroken family members held a vigil for one of the two men killed in the East Village building explosion and fire last week, as investigators shift their focus to what caused the blast.

Nicholas Figueroa, 23, was a bowling alley worker who had gone on a date to Sushi Park, on the ground floor at 121 Second Ave. just north of Seventh Street. The explosion on Thursday afternoon went on to level the building, as well as its neighbors at 119 and 123 Second Ave.

His body has been identified by relatives. Another body found in the rubble was believed to be 26-year-old Moises Locon, a busboy at the sushi restaurant.

About 100 people gathered near the building Monday night to mourn Figueroa.

“It’s a tragedy what happened to my brother,” the victim’s brother said to the crowd. “We loved him. He was such a good kid.”

The devastated family members thanked those who worked tirelessly to find Figueroa’s body. They released white balloons as the crowd applauded.

“We had faith you guys was going to find my brother,” the victim’s brother said. “We thank you.”

Also in the crowd was Therese Galarce, the woman with whom Nick Figueroa was on a date at Sushi Park when the explosion happened.

She somehow returned to the scene Monday, with bruises still visible around her eyes.

Nick Figueroa’s mother and father also said a few words.

Sultan Bagudu — Nick Figueroa’s former roommate at SUNY Buffalo State — also talked about his friend to CBS affiliate WIVB-TV, Buffalo. Figueroa graduated from the upstate school in December with a degree in criminal justice.

Bagudu told the station that his former roommate had a quirky personality and could turn anything into a joke.

“He would say something pretty ridiculous. And everybody would just laugh,” Bagudu told WIVB.

Bagudu was also in New York City at the time of the explosion, but did not know Figueroa was at Sushi Park when the explosion happened, WIVB reported.

“It could have been avoided. Like he could have simply maybe went to another restaurant. Or maybe went to that same place maybe an hour later or an hour earlier,” told WIVB.

His family said they now want justice for his death.

“He was beautiful. I can’t wait until I see my son again so I can hold him, kiss him and tell him I love him,” said Figueroa’s father.

“He came out in one piece, and that’s the most we can ask for, that’s what we were praying for,” said Figueroa’s mother, Ana.

INVESTIGATORS PROBE CAUSE OF EXPLOSION

Meanwhile, with the two bodies recovered, investigators have shifted their focus to the cause of the blast.

Mayor Bill de Blasio has said someone may have improperly tapped a gas line before the explosion. Consolidated Edison said workers discovered in August that a line had been illegally tapped.

By the hour, crews continue to get closer to the basement and gas line where officials believe the explosion originated, retracing what they describe as fatal missteps before the blast.

Once investigators have access to the basement, they’ll try to pinpoint the cause of the explosion. City officials suspect that leaking natural gas was the source of Thursday’s explosion and fire, which sparked a raging blaze that took hundreds of firefighters to quell.

The FDNY said Con Ed inspectors and fire marshals are expected to gain access to the cellar on Tuesday, CBS2’s Matt Kozar reported.

“When we reach the level of the gas piping, the way the debris is removed will change so that those who will investigate the mechanics of what happened will have access to that without it being torn apart,” Fire Commissioner Daniel Nigro said.

PHOTOS: East Village Explosion

Plumbers in the basement may have made an illegal connection from the building’s gas line to feed through newly installed piping, sources told CBS2.

Inspectors from Con Ed had visited that building about an hour before the explosion and determined work to upgrade gas service didn’t pass inspection, locking the line to ensure it wouldn’t be used and then leaving, officials said.

Fifteen minutes later, the sushi restaurant’s owner smelled gas and called the landlord, who called the general contractor, Chief of Detectives Robert Boyce said. Nobody called 911 or Con Ed.

“When they smelled the gas, the restaurant owner called the owner of the building, which was a major mistake. They should have called 911. We don’t know what the outcome would have been,” said Joseph Esposito, commissioner of the city’s Office of Emergency Management.

The contractor, Dilber Kukic, and the owner’s son went into the basement and opened a door, and then the explosion happened, burning their faces, Boyce said. Kukic, who has pleaded not guilty to an unrelated charge of bribing a housing inspector, declined through his lawyer to comment on the circumstances surrounding the explosion.

De Blasio said the Manhattan district attorney’s office is investigating the blast, 1010 WINS’ Al Jones reported.

When asked if the explosion will spark a change in regulations or tougher penalties, Mayor de Blasio said “First we have to complete the investigation to see what that shows us about what happened here.

“I think that’s going to give us a good sense of whether we see something that might indicate any kind of policy changes, but right now we just don’t know the details enough to draw that conclusion,” the mayor added.

Twenty-two people were injured in the explosion, four critically. By Monday, three of those four in critical condition had been released from the hospital, Kozar reported.

The two bodies were discovered about two hours apart Sunday afternoon.

“We continue to search although there are no other missing persons so the feeling is everyone who had been reported missing has now been found. The likelihood of anyone else being here is very small,” Nigro said.

The Manhattan District Attorney’s office is also involved – suggesting that criminal charges are likely, WCBS 880’s Marla Diamond reported.

Meanwhile, four days after the blast, dozens remain out of their homes, and businesses are struggling to get customers as the community tries to move forward.

“It’s like an era that’s gone,” an East Village resident said. “It’s a finished time.”

“It is very stressful, it’s very scary and some of the kids are having a hard time with it. It’s gonna be a challenge,” resident David Wellman said. “The whole neighborhood feels it because you feel it all through the neighborhood, not just on Second Avenue.”

At least 80 of the 141 families that had been evacuated after the blast have been allowed to return home.

(TM and © Copyright 2015 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2015 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)