NEW ORLEANS  — Police have been trying to figure out what sparked a gun battle in a crowded New Orleans park that left 16 people wounded and the mayor is calling on witnesses to come forward.

Hundreds of people were gathered at a playground for a block party and music video shoot when two groups in the crowd opened fire on each other Sunday evening, police said.

Police were on their way to break up a big crowd at Bunny Friend Playground when gunfire erupted at the park in the city’s 9th Ward, the police said in a statement.

New Orleans Mayor Mitch Landrieu, speaking in a news conference called on people who were in the park to come forward with information. The police have also asked people who might have any video of the shooting to bring it to police.

“At the end of the day, it’s really hard to police against a bunch of guys who decide to pull out guns and settle their disputes with 300 people in between them. That’s just not something you can tolerate in the city,” Landrieu said.