CHATSWORTH ( — State and local regulators announced Thursday that a well that had been leaking natural gas over Porter Ranch for 16 weeks has been permanently sealed.

Jason Marshall of the California Department of Conservation declared that the Aliso Canyon storage facility owned by Southern California Gas Co. is no longer emitting methane. “We have good news. The division of oil and gas has confirmed that the leak at the Aliso Canyon storage field is permanently sealed.”

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The gas company said the 60-year-old well was plugged with cement, and several tests showed no more gas was coming out.

Los Angeles County Interim Health Officer Dr. Jeffrey Gunzenhauser said it is now safe for Porter Ranch residents to return home. “Once the gas is completely gone, the odorant will dissipate and will no longer cause those symptoms.” He said air samples taken from the storage field and from neighborhoods show extremely low levels of contaminants.

State regulators said air samples will continue to be taken daily, and a comprehensive investigation is underway to figure out what caused the leak.

In the meantime, no more gas will be injected into the underground reservoir until all of the 114 remaining wells are inspected using new standards.

Michael Picker is President of the California Public Utilities Commission. He said the Aliso Canyon storage facility is essential in preventing natural gas shortages during peak periods. “We may not be able to get all the gas that we want or need. That’s why it’s important to have that local storage.

Picker said the PUC has also been investigating reports of unusually high gas bills, and that SoCal Gas can not hike the rates without all five commissioners’ approval.

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“There are some folks who have seen higher bills. I think that our tracking shows that is likely caused by the very cold winter that we’ve had,” Picker said.

People who have relocated will have until a week from Thursday to move back home. SoCal Gas said leases will also be honored, and special accommodations will be made for those with special circumstances.

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Nearly 6,500 families have relocated to hotels or rental homes since the massive leak was detected in late October. They complained of headaches, nausea, dizziness and nosebleeds.

The Los Angeles Unified School District said it will begin making arrangements for students to return to Porter Ranch-area schools despite initial plans to relocate through the end of the school year.

SoCalGas pleaded not guilty Wednesday to misdemeanor charges involving reporting of the leak to authorities and discharging contaminants into the air.

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The utility has been hit with at least 67 lawsuits, penalties from government agencies and expenses to mitigate pollution.