A group of Los Angeles city firefighters on Tuesday filed a lawsuit against Southern California Gas Co. (SoCalGas), alleging they were potentially exposed to hazardous toxins during a massive methane leak three years ago at the Aliso Canyon underground natural gas storage facility.

The lawsuit against the Sempra Energy unit, the nation’s largest gas-only utility, was filed in state Superior Court in Los Angeles concerning a leak at Aliso Canyon, which is on the northern edge of the city in the San Fernando Valley.

The filing came almost three years to the day after the leak was identified. It continued for nearly four months and ultimately cost SoCalGas more than $1 billion. Twenty-nine firefighters in their lawsuit allege that the utility carried out a “massive disinformation campaign” that understated the public health risks to residents and public agencies.

The plaintiffs are seeking unspecified damages and fees, contending that they have suffered from severe headaches, nosebleeds, skin rashes, dizziness and breathing difficulties, and some of the plaintiffs are battling cancer.

During the leak, firefighters helped utility employees, contractors and residents who became sick during the blowout and were forced to abandon their homes. A subsequent county Department of Public Health set of tests of nearby homes concluded indoor conditions “did not present a long-term health risk,” so residents were allowed to return home, a SoCalGas spokesperson said.

SoCalGas on Wednesday reiterated that employees had historically worked alongside first responders, including firefighters, and said it maintained the “utmost respect and appreciation for their hard work, professionalism and dedication to safety.”

The utility also stressed that “thousands” of air, soil and dust samples were tested during the prolonged leak and for months thereafter, which concluded “there was and is no long-term risk to public health or safety.”

Residents, environmental groups and some local government officials have disagreed about the findings.

In a June filing with the U.S. Securities and Exchange Commission, SoCalGas and Sempra said the leak has cost an estimated $1.014 billion, 55% attributable to paying for temporarily relocating thousands of residents from the Porter Ranch development south of the 3,600-acre underground storage field.

SoCalGas also noted in the filing that $987 million of the estimated costs have been covered by insurance. However, it said costs related to the leak are likely to grow because as of Aug. 1, 382 lawsuits were pending involving 48,000 plaintiffs against the utility and/or its parent company.