A shooting in the engineering building at Brown University on Saturday has left at least two people dead and eight critically injured, the mayor of Providence, R.I., said.

The Ivy League school in Rhode Island issued an active shooter alert late in the afternoon, urging students and staff to take shelter.

Police have yet to release details about the number of victims, their conditions or the circumstances of the shooting.

Providence Mayor Brett Smiley announced the number of casualties in a news conference Saturday evening. The university confirmed the numbers on its website.

University officials initially told students and staff that a suspect was in custody, but later said that was not the case and police were still searching for a suspect or suspects, according to alerts issued through Brown's emergency notification system.

"We're still getting information about what's going on, but we're just telling people to lock their doors and to stay vigilant," said Providence council member John Goncalves, whose ward includes the Brown campus.

"As a Brown alum, someone who loves the Brown community and represents this area, I'm heartbroken. My heart goes out to all the family members and the folks who've been impacted."

The reported shooting occurred near the Barus & Holley building, a seven-storey complex that houses the university's school of engineering and physics department where final exams were taking place Saturday. According to the university's website, the building includes more than 100 laboratories, dozens of classrooms and offices.

Saturday was the second day of final exams for the fall semester.

U.S. President Donald Trump said he has been briefed on the shooting.

"God bless the victims and the families of the victims!" he said on his social media site.

Students were urged to shelter in place as police responded to the scene, and people were told to avoid the area. A police officer warned media to take cover in vehicles because the area was still an active scene.

Officials cautioned that information remained preliminary as investigators worked to determine what had occurred.

Police were actively investigating and still gathering information from the scene, said Kristy dosReis, chief public information officer for the City of Providence. The FBI said it was assisting in the response.

Brown is a private institution with roughly 7,300 undergraduate students and more than 3,000 graduate students.