The blast lifted the roof off the Waukegan shopping centre

Aerial footage

Hydraulic lifting equipment was used to rescue the injured after the roof was blown off the plaza in Waukegan, about 65km (40 miles) north of Chicago.

Waukegan Mayor Richard Hyde told the BBC the blast was caused by a gas leak around noon local time (1800 GMT).

Four shops were damaged as a ceiling collapsed and shop windows shattered in the blast.

Around 100 firefighters rushed to the scene, with fire crews drafted in from surrounding towns to help with the rescue effort.

A team from the People's Gas company were on site to investigate the suspected gas leak.

The worst-hit shops included a hair salon, a mobile phone shop and a tailoring shop.

Mannequins strewn among debris from the blast were at first mistaken for the body of victims, says the BBC's Jonathan Josephs.