LOS ANGELES (AP) — Los Angeles County public health officials are seeking independent researchers to study the short- and long-term effects of the nation's largest-known natural gas leak on the health of people who lived in nearby communities.

The county Department of Public Health announced the solicitation, formally known as a request for proposals, in a statement Tuesday.

“We are committed to selecting an independent research group with the broad but also highly specialized expertise needed to shed further light on the health impacts of this catastrophic environmental disaster,” said Dr. Paul Simon, chief science officer.

Thousands of families were sickened and had to leave their homes due to the 2015 blowout at Southern California Gas Co.'s gas storage facility in the Santa Susana Mountains on the northern edge of Los Angeles.

More than 120,000 tons (109,000 metric tons) of methane gas were released into residential communities surrounding the facility over 111 days.

The Aliso Canyon Disaster Health Research Study will be conducted under a scientific oversight committee and funded with $25 million secured under a consent decree between SoCal Gas and city, county and state governments.

A 2021 settlement of up to $1.8 billion with SoCal Gas and its parent company, Sempra Energy, will compensate 35,000 plaintiffs.