A routine maintenance procedure may cause a noticeable odor of natural gas over parts of north Lawrence on Friday, according to Black Hills Energy.

The ICL Performance Products plant, 440 N 9th St., plans to purge its gas lines sometime Friday before coming back online from its annual scheduled shutdown, Black Hills spokeswoman Monique Pope said. The lines had previously been purged on April 30 when the plant was shut down for repairs, resulting in a widespread odor that prompted several calls to emergency services.

Black Hills, which has a support contract with ICL, helps conduct tests and repairs at the plant.