LOS ANGELES—An urban oil field blamed for causing chronic respiratory illnesses and nosebleeds in a South Los Angeles neighborhood will be modified to prevent leaks and decrease pollution.

The Los Angeles Times reports ( http://lat.ms/1hddbVU) Sunday that Allenco Energy Co. plans to upgrade its air pollution control systems, inspect and repair tanks, and make other changes.

The company voluntarily suspended operations Nov. 22 at the request of California Sen. Barbara Boxer. Since then pollution and reports of respiratory ailments have dropped.

Allenco is under investigation by the U.S. Environmental Protection Agency, the South Coast Air Quality Management District, the city attorney's office and the Archdiocese of Los Angeles.

The Los Angeles County Department of Health has called for a comprehensive audit of the facility to better determine the health hazards its poses.