LOS ANGELES (Reuters) – Methane fumes spewing from a ruptured underground pipeline near a Los Angeles neighborhood hastened the demise of an elderly woman already suffering from lung cancer, her family said in the first wrongful death claim stemming from the gas leak.

The lawsuit seeks unspecified monetary damages against Southern California Gas Co, a division of San Diego-based Sempra Energy, for the suffering and death of Zelda Rothman, 79, who died on Jan. 25, about three months after the leak was detected.

Rothman, who lived about 3 miles from the source of the escaping methane at the Aliso Canyon natural gas storage field, was leading an active life, despite her diagnosis of stage 4 lung cancer, her family’s lawyer, Scott Glovsky, said on Thursday.

“She was going on cruises, and going out to lunch with friends and driving,” Glovsky said.

Her fragile condition began to worsen in the weeks after the leak began as she suffered from increasingly labored breathing and extreme headaches, requiring round-the-clock oxygen support by December, according to the lawsuit.

Rothman, a decades-long resident of the Porter Ranch community where thousands of residents have been temporarily relocated at the utility’s expense, was moved into a hospital after her adult children visited in December, Glovsky said.

The complaint blames her rapid decline on exposure to methane, the principal component of the escaping natural gas, and other contaminants within the gas. Ranked as the largest such gas leak ever in California, it accounted for a fourth of all methane emissions statewide at its peak.

“We’re not claiming the gas company caused (Rothman’s) cancer,” Glovsky said. “We’re claiming they essentially poisoned her and hastened her death and destroyed the quality of her life in the time she had left.”

The lawsuit, filed on Tuesday, asserts the utility could have halted the leak soon after it was detected if the ruptured well were equipped with a “sub-surface safety valve,” which the complaint said the company removed in 1979.

“We are sorry to hear about the family’s loss,” company spokeswoman Kristine Lloyd said of the wrongful death claim. “We are reviewing the lawsuit and will allow the judicial process to take its course.”

More than 20 lawsuits against SoCal Gas have been filed by residents over the leak, along with civil claims by Los Angeles city and county, the state of California and air quality regulators. County prosecutors filed criminal charges on Tuesday.

(Reporting by Steve Gorman; Editing by Peter Cooney)