Gas and electric companies agreed to pay a $5 million fine to the U.S. Department of Energy on Wednesday after a federal investigation found they had knowingly allowed methane to leak from underground pipelines.

The $5.9 million settlement with New Jersey-based Gas-Electric Energy Services (GES) is the largest of its kind in U.K. history and will give the company a boost in its effort to reduce methane emissions from its underground facilities, according to the company.GES said it was pleased to have resolved the matter and said it is working with the U, EPA and other government agencies to ensure that the company complies with existing and future federal regulations.

It also said it will work with the New Jersey Public Service Commission to develop a comprehensive mitigation plan to address methane leaks.

The agreement comes after the U’s Department of Justice, the U to the Environment, the National Oceanic and Atmospheric Administration and other federal agencies issued a joint statement in December saying that methane leaks from gas and electric plants posed a “serious threat to public health and safety.”

The companies are expected to pay about $7.7 million in penalties.

The companies’ response came as regulators in the U and elsewhere have raised concerns about the gas and electricity industry’s practices and the possibility of a pandemic.

The U.N. agency has warned that a pandemics pandemic could cause “the widespread destruction of the human and environmental systems of the Earth and the collapse of the entire economic and financial system.”