Providence, Rhode Island - A person detained over the shooting that killed two students at Brown University was to be released, officials said on Sunday, adding the manhunt had resumed for a suspect.

A shooter opened fire on Saturday at the elite Ivy League university in Providence, Rhode Island, in a building where exams were taking place, triggering a campus lockdown and launching an hours-long hunt for the suspect.

US authorities early on Sunday detained a person of interest in the mass shooting that also wounded nine others, the latest in a long line of school attacks across the country.

Brown University President Christina Paxson confirmed in a letter to community members that all 11 victims were students.

Murder Brown University on lockdown after shooter kills multiple people during exams

"Shortly, we will be releasing the person of interest who had been detained earlier today," Providence Mayor Brett Smiley said on Sunday.

"I think it's fair to say there's no basis to consider him a person of interest," Rhode Island Attorney General Peter Neronha told reporters. "That's why he's being released."

Officials said they'd continue to pursue a suspect but provided few details on how the investigation has progressed.

"Obviously we have a murderer out there, frankly, and so we're not going to give away the game plan," Neronha said.

Police released 10 seconds of footage of the suspect, seen from behind, walking briskly down a deserted street after opening fire inside a first-floor classroom.