(CNN) -- Three faculty members were killed and three other school employees were wounded Friday in a shooting at the University of Alabama in Huntsville, a school spokesman said.

A female shooting suspect was in custody and a second person was detained, "not arrested," spokesman Ray Garner told reporters.

Huntsville Police Chief Henry Reyes left open the possibility that more than one person had been detained. "We have a suspect and possible persons of interest," he said late Friday. "Until we go through everything, we're not going to say exactly how many or who we have."

He said police were questioning the suspect, whom he would not identify.

Of the wounded, two were faculty members and the third was a staff member, he said.

Garner said the incident occurred shortly before 4 p.m. in Shelby Hall. Police arrived at 4:01 p.m.; residence halls were locked down at 4:10 p.m.; the building was secured by 5:45 p.m., he said.

The suspect was taken into custody outside the building, said Reyes. No weapon has been recovered, he said.

The 6-year-old, $60 million facility houses the chemistry department and is named for U.S. Sen. Richard Shelby of Alabama and his wife, Annette Shelby.

Garner identified the dead as Gopi Podila, chairman of the biological sciences department; Maria Davis, associate professor of biology; and Adriel Johnson, associate professor of biology.

He identified the injured as Joseph Leahy, associate professor of biology, in critical condition; Luis Cruz-Vera, assistant professor of biology, in stable condition; and Stephanie Monticello, staff assistant, also in stable condition. The wounded were taken to Huntsville Hospital.

Classes and athletic events are to be canceled February 15-19, he said.

Asked why students had not been alerted for more than an hour after the shootings, Reyes said, "I can't comment on that part."