Providence police have detained a "person of interest" in connection with the Brown University shooting that left two students dead and another nine people wounded at the US Ivy League school.

Kristy DosReis, chief information officer for public safety, told Reuters that a person of interest was in police custody following the shooting.

Oscar Perez, Providence’s police chief, told reporters a suspect was taken into custody early Sunday and they are not seeking anyone else at this time.

Authorities declined to share details about the individual as the probe remains active.

Seven people injured at Brown University are in stable condition, Providence Mayor Brett Smiley said. One remains in a critical but stable condition, while another has been discharged, he added.

Smiley said the shelter-in-place order for nearby neighborhoods was lifted after the arrest but some streets remain shut as investigators work at the scene. Residents should expect a visible police presence across the city, he said.

"The people of Providence should breathe a little easier this morning," Smiley added.

Brown said on Sunday that police had also lifted a shelter-in-place order for its campus in Rhode Island.

More than 400 law enforcement personnel were deployed on Saturday as police sought a suspect who had entered a building where students were taking exams with a firearm.

Access to parts of the campus remained restricted on Sunday as police maintained a security perimeter around Minden Hall and nearby apartment buildings, said Brown, which has hundreds of buildings, including lecture halls, laboratories and dorms.

Streets around the campus had been packed with emergency vehicles on Saturday while law enforcement agencies sought the gunman.

Agents from the Federal Bureau of Investigation and the Bureau of Alcohol, Tobacco, Firearms and Explosives were working with local and state police.

Officials released a video of a suspect, a male possibly in his 30s and dressed in black. Providence Deputy Police Chief Timothy O'Hara said on Saturday the individual may have worn a mask, but officials were not certain.

Investigators retrieved shell casings from the scene, O'Hara added.

The gunman fled after shooting students in a classroom in Brown's Barus & Holley engineering building, where outer doors had been unlocked while exams were taking place, officials said.

Brown President Christina Paxson told reporters that all or nearly all of the victims were students, adding: "This is the day one hopes never happens, and it has".

Under desks for hours

As news of the shooting spread, the school told students to shelter in place.

Brown student Chiang-Heng Chien told local TV station WJAR he was working in a lab with three other students when he saw the text about the active shooter situation a block away. They waited under desks for about two hours, he said.

Rhode Island Governor Daniel McKee vowed that the shooter would be brought to justice.

President Donald Trump told reporters at the White House on Saturday that he had been briefed on the situation, which he called "terrible."

Compared to many countries, mass shootings in schools, workplaces, and places of worship are more common in the US, which has some of the most permissive gun laws in the developed world. The Gun Violence Archive, which defines mass shootings as any incident in which four or more victims have been shot, has counted 389 of them this year in the US, including at least six such shootings at schools.

Last year, the US had more than 500 mass shootings, according to the archive.