Several members of the Duenas family are suing over allegations that the defendants were negligent, created a public nuisance and trespassed, among other things.
"This is a case where a house blew up, so you're going have life-altering injuries," said attorney Niall McCarthy of Cotchett, Pitre & McCarthy. "We're trying to get them to as close to normal as possible, trying to get as much of their old life back as possible."
EXCLUSIVE: Brother shares how siblings escaped Hayward gas line explosion
EXCLUSIVE: Brother shares how siblings escaped Hayward home explosion
On Dec. 11, the day of the explosion, Jesus Duenas Ponce, his sister Maria del Socorro Duenas Ponce and her adult daughter Soledad Flores, were at the home they were renting in the 800 block of East Lewelling Boulevard in the unincorporated Alameda County community of Ashland.
Two other plaintiffs, brother Jorge Duenas Ponce and del Socorro Duenas Ponce's son, weren't at home that morning.
At about 7:25 a.m., a crew working for Mayo Asphalt Milling struck and damaged a gas service line while performing excavation work, according to the suit.
Mayo Asphalt was a subcontractor to another defendant, Redgwick Construction Co., which was hired by Alameda County to work on its East Lewelling Boulevard upgrade project.
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The Mayo Asphalt crew notified PG&E about the damaged pipeline and the utility then sent people out to isolate the damaged line and stop the flow of gas, which was done by 9:25 a.m.
The Alameda County Fire Department also responded but left the area soon after when a PG&E employee said they didn't need assistance, according to a National Transportation Safety Board investigation into the blast.
At 9:37 a.m., an explosion leveled the Duenas' home and significantly damaged at least two others.
WATCH: Shocking video shows massive Hayward building explosion after gas line rupture; 6 injured
Massive Hayward building explosion after gas line rupture; 6 injured
"For more than two hours, these defendants knew gas was leaking near this family's home, and not one of them knocked on the door and told the Duenas family to leave," McCarthy said.
Flores and del Socorro Duenas Ponce were asleep at the time and were both injured when a wall collapsed on them, according to the suit.
The mother suffered a fractured neck, burns to her hands, arms and face, injuries to her throat and jaw, and required a breathing machine and multiple surgeries.
Her daughter's two broken ribs required surgery.
Duenas Ponce broke several bones when he was thrown into the basement by the explosion and was burned extensively as he crawled out of the debris on his belly, according to the suit.
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He has undergone multiple surgeries and continues to have limited mobility and limited use of his hands, according to the suit, which says the family also lost all of their belongings.
According to the NTSB investigation, a PG&E crew said they knocked on the Duenas' door and on the doors of two neighboring houses but no one responded.
The suit says this claim is false and is contradicted by the family's own account and by video evidence from a neighbor's camera and "that PG&E made the false statement to cover up its failure to notify residents."
A PG&E spokesperson said the company is reviewing the suit but declined to comment on specific allegations.
"The National Transportation Safety Board's investigation process is ongoing and as a party to the investigation we are restricted from commenting further at this time under NTSB rules," said PG&E spokesperson Tamar Sarkissian.
Representatives for Alameda County and its construction companies didn't immediately respond to a request for comment, nor did the property owner, who is also named in the suit.