At least 32 people have been injured in three US cities as Americans celebrated the Fourth of July weekend. Chicago, Indianapolis and Houston were all affected, with four people being shot at a music festival in the Texan city.

The Houston Caribbean Festival attracted 5,000 visitors, according to the city’s police spokesperson, Jodi Silva. However, at around 2am on Saturday morning, a man opened fire inside the arena, according to an eyewitness.

One of the four who were shot is in critical condition, Silva added, while two women were injured after people started to panic and began fleeing the building where the event was taking place. The gunman is still at large.

One witness, Deion Woodson, said, "It's usually a friendly Caribbean fest, everybody have fun, but this time one person started fighting and that's basically what happened and started shooting."

There were 30 off-duty police officers working at the festival, though none were hurt.

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Seven people were shot and wounded in Indianapolis early on Saturday evening, with one in critical condition, Reuters reports. The incident happened in the city’s night club district, after an argument broke out between two people, local police said.

No suspects were in custody and the shooting remained under investigation, according to a Twitter posting from the Indianapolis police.

The 2:20 am shooting apparently started after two people bumped into each other at a bar or on the sidewalk and began arguing, according to media coverage of a police press conference. A spokesman for the police department did not return calls on Saturday seeking confirmation.

The violence broke out in the city’s Broad Ripple district, a stretch of bars, restaurants and entertainment venues.

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Chicago saw some of the worst violence on the Independence Day weekend, with at least 21 people shot Saturday night, bringing the total number of people wounded in the city to at least 36 since the holiday weekend began Thursday afternoon, the Chicago Tribune reported.

The paper added that three of the incidents involved police shootings.

During last year’s Fourth of July weekend, shootings in Chicago left at least 12 people dead and more than 62 wounded, NBC's local Chicago affiliate reported at the time.

Chicago Mayor Rahm Emanuel has called gun violence the city's “most urgent problem.”

The US averages 87 gun deaths a day, with an average of 183 gun-related injuries.