CHICAGO — Two people were arrested after a small -- and likely deliberate -- explosion at a high school injured a staff member in Memphis, Tennessee Thursday, police said.

The explosion happened shortly after a bomb threat was called into Craigmont high school around 11:20 am (16:20 GMT).

"After receiving the threat, members of the school staff heard a loud noise and saw fumes," Memphis police said in a statement.

One of the staff members was taken to hospital in "non-critical" condition after inhaling the fumes but no other injuries were reported, police said.

Students were evacuated from the building and the bomb unit was sent into to search the building for any other devices and help clear up the damage.

A spokeswoman for the police declined to confirm local media reports that the two people in custody are students.

"More information will be available as soon as the suspects are charged," Sergeant Karen Rudolph told AFP.

A second home-made bomb went off in the parking lot of a grocery store in the nearby town of Arlington Thursday, WREG reported, but nobody was injured.

The device was reported placed in a shopping cart that was pushed towards the store and exploded before it reached the building.