Seven people are dead and 33 others injured following four separate late night and early morning mass shootings in Ohio, South Carolina and New Jersey, authorities said Sunday.

The dead include two girls, ages 14 and 16, police said. No arrests had been made in any of the incidents as of Sunday morning, according to authorities in each state.

A house party in Cumberland County, New Jersey, was one of the most violent events, in terms of victims. There, state police say, a 30-year-old man and a 25-year-old woman were fatally shot and 12 other adults were taken to area hospitals for gunshot wounds sustained just before midnight Saturday. One of those injured was last reported as being in critical condition, police said. 

“No arrests have been made, and the motive and incident remain under investigation,” the state police department said in a statement Sunday.

In South Carolina, a 14-year-old girl was fatally shot and 13 others wounded after a fight broke out at an unauthorized outdoor concert taking place around 10:30 p.m. Saturday in North Charleston, local station WCSC reported.

A few hours later, around 2 a.m. Sunday, a shooting outside a bar in Youngstown, Ohio, left three people dead and three others wounded, police there said. A motive for the violence was not immediately released by police, who said they are still talking to several individuals and investigating the scene.

And just before midnight Saturday, a shooting involving teenagers in Columbus, Ohio, left a 16-year-old girl dead and five other teens wounded. Two other teenagers were taken to hospitals for non-gunshot injuries sustained while attempting to flee the scene, police said.

The teenagers were participating in a music party that had been promoted on social media at a downtown amphitheater when shots rang out just before midnight, The Columbus Dispatch reported.

Mass shootings, which are identified as events where at least four people are shot, not including a shooter, have risen significantly over the last few years in the U.S., according to records kept by the nonprofit research group the Gun Violence Archive.

Last year, there were more than 600 mass shootings reported, while 2019 saw 417, which was up from the 337 reported in 2018. This year is also setting itself up to be a significantly violent one, with 223 mass shootings recorded as of this month, according to the GVA.