School is in session today after a bomb threat called into Austin’s Southgate Elementary School Tuesday evening forced a police sweep and a lock-down at the school Wednesday morning.

Police searched identified areas Wednesday morning — while some students and staff were relocated to the library. Police did not find a bomb and gave an “all clear” about 45 minutes later, according to Austin Police Lt. John Mueller.

The school day then resumed as usual and a letter was sent home to parents explaining the incident, superintendent David Krenz said.

The bomb threat had been left on the school’s voicemail system Thursday, identifying two different locations at the school, Krenz said.

The message was first heard Wednesday morning by a secretary who informed principal Edwina Harder. Harder then called Krenz and an Austin police liaison officer who notified dispatch.

The report was taken by police at 8:57 a.m., Mueller said. School begins at Southgate at 8:10 a.m.

The caller sounded like an elementary-age child, and the police investigation was ongoing as of Thursday morning, Mueller said.

Mueller would not comment on whether any Southgate students are suspects.

Austin Public Schools complete at least five drills a year for emergency lock-down procedures, Krenz said.

“In these situations we follow our emergency planning procedures and we will again evaluate and review these policies following this incident,” Krenz said.

—Mike Rose contributed to this report.