HOUSTON (KIAH) — Austin High School in southeast Houston has lifted its precautionary lockdown after two hours for an unknown threat, according to Houston ISD officials.

School principal Orlando Reyna said in a statement that Austin High School put the campus in a lockdown around 10:30 a.m. Thursday due to a threat from outside the campus.

Then just after noon, Reyna announced that the lockdown was lifted after receiving an all-clear signal from police.

 “Our students are safe, our building is secure, and our instructional day continues normally,” Reyna said in a statement.

The lockdown meant that no one is allowed on campus. Parents were asked to wait until the lockdown is lifted to drop or pick up their child at the school.

The lockdown comes two days after a shooting at Robb Elementary School in Uvalde on Tuesday that left 19 children and two teachers dead.