A biology professor at a southern US university has been charged with murder over the shooting dead of three fellow biology professors at the campus.

Authorities said Amy Bishop of the University of Alabama's Huntsville campus opened fire during an afternoon faculty meeting, killing the three and injuring three other school employees.

Bishop was charged with one count of capital murder, which means she could face the death penalty if convicted.

Bishop was taken in handcuffs from a police precinct to the county jail and could be heard saying: "It didn't happen. There's no way... they are still alive."

Police said they were also interviewing a man as "a person of interest".

University spokesman Ray Garner said the three killed were Gopi K Podila, the chairman of the Department of Biological Sciences, and two other faculty members, Maria Ragland Davis and Adriel Johnson.

Two others are in critical condition, and a third who was wounded was upgraded to fair condition.

The injured were identified as department members Luis Cruz-Vera, who was listed in fair condition and Joseph Leahy, in critical condition in intensive care, and staffer Stephanie Monticello, also in critical condition in intensive care.

No students were harmed in the shooting.

Bishop, a neurobiologist from Harvard University, joined the university's biology faculty as an assistant professor in 2003.

The Huntsville campus has about 7,500 students in northern Alabama, not far from the Tennessee border. The university is known for its scientific and engineering programmes and often works closely with Nasa.