PRINCETON, Ind. (AP): Officials still haven’t determined the source of methane gas that forced about 30 people to evacuate a southwestern Indiana apartment complex more than two weeks ago.

The tenants were forced from the Tower Manor apartments in Princeton on April 29 after people reported a gas odor.

Indiana Department of Natural Resources spokesman Jack McGriffin tells the Princeton Daily Clarion that gas levels have remained too high for drilling work to find the source.

Officials have said the gas might have come from a 1920s-era abandoned coal mine that’s an estimated 400 feet below ground in the city about 25 miles north of Evansville.

Some residents stayed for a time in a temporary shelter at the Gibson County Fairgrounds. No injuries were reported from the gas.