None of the gunshot wounds were life-threatening, the Jasper County Sheriff's Office said in a statement that offered few other details about the shooting at a residence in Jasper, a town of about 7,200 people some 134 miles (215 km) northeast of Houston, Reuters reported.
The victims were taken to two hospitals, the sheriff's office said, without reporting on the number of shooters.
"This investigation is ongoing and people of interest are being questioned," the statement said.
The victims ranged in age from 15 to 19, KBMT-KJAC television news reported.
Jasper High School held its prom, a right of passage for American secondary schools, at a church meeting hall on Saturday night, the TV news reported.
The superintendent of the Jasper Independent School District, John Seybold, pledged full cooperation with any law-enforcement investigation "to bring these perpetrators to justice."
"There will be a much larger law enforcement presence this week to ensure student safety, as well as counselors on hand for any students who need their assistance," Seybold said in the statement as reported by local media.
A week ago, four people were shot dead and 32 wounded at an Alabama "Sweet 16" birthday party in the small town of Dadeville. Five suspects have been charged with murder in that shooting.
Firearms have become the leading cause of death for US children and teens, surpassing motor vehicle accidents, the US Centers for Disease Control and Prevention reported last year.