Relatives of the couple who died after a house fire near San Benito on Christmas Day have hired an attorney and filed a $500 million lawsuit alleging negligence.

The lawsuit accuses the various companies of negligence that contributed to the Christmas Day blaze that killed a couple and left six others injured.

Houston-based attorney Tony Buzbee is representing Olivia Pulido in the lawsuit filed against Hino Gas Sales, Inc., Rego Products, Inc., Engineered Controls, Inc., Thompson Tank, Inc., La Pulga De Rio and Lowe’s Home Centers, L.L.C.

Pulido is the mother of Juan Ramon De Leos, who died after the fire with his wife Genesis Moreno De Leos.

Buzbee claims that an explosion was caused by a propane gas leak and was so strong it blew the home’s roof off.

“There was 100 percent no reason this should’ve happened. It’s pretty clear that Hino Gas did not do what it was required to do by law,” Buzbee said.

Vice president of the Hino Gas Company, Alex Hinojosa, Jr., though, tells a different story.

“The roof fell in which means the fire started in the attic, which means it was probably an electrical fire. There wasn’t an explosion,” Hinojosa said.

Buzbee said Hino Gas should never have filled up the propane tank, which he claims was improperly positioned and installed. Hinojosa, however, told CBS 4 News that the company is not required by the Texas Railroad Commission LP Gas rules to perform a pressure test if the tank already has gas. He said this was the case when it was filled more than a year before the blaze.

“As far as we know, all the allegations will be proven to be not true,” Hinojosa said.

The Cameron County Fire Marshal’s Office still has the cause of the fire listed as undetermined.

Buzbee said company workers for Lowe’s Home Improvement did not properly cap the gas line after they removed two gas appliances from the home and replaced them with electric appliances.

A representative for Lowe’s told CBS 4 News they do not comment on ongoing lawsuits.