A tornado warning remained in effect Friday night for northwestern Livingston and southern La Salle counties until 9:45 p.m., the National Weather Service Chicago/Romeoville said.

At 9:11 p.m., a severe squall line capable of producing tornadoes and extensive straight-line wind damage was located along a line extending from near Grand Ridge to near South Streator to Flanagan to near Gridley, moving east at 45 mph, the weather service said.

The warning was based on radar-indicated rotation, according to the alert.

Flying debris poses a danger to those without shelter. Mobile homes could be damaged or destroyed, and damage to roofs, windows and vehicles is expected. Tree damage is likely, the weather service said.

The warning affected Streator, Pontiac, Marseilles, Seneca, Flanagan, Wenona, South Streator, Grand Ridge, Cornell, Ransom, Rutland, Kangley, Long Point, Dana and Leonore.

Residents were urged to move to a basement or an interior room on the lowest floor of a sturdy building and avoid windows. Those outdoors, in mobile homes or in vehicles should move to the closest substantial shelter and protect themselves from flying debris.

The weather service cautioned that residents should not wait to see or hear a tornado before taking cover.