GRAPEVINE,Texas (CBSDFW.COM) – Grapevine Colleyville ISD schools returned to the classroom Monday morning following a string of shooting and bomb threats last week.

At Cross Timber Middle School a Grapevine Police cruiser was on patrol all day. Increased police presence is one measure the district is taking not only at Cross Timber but also at Glenhope Elementary and Grapevine Middle schools.

In response to threats the schools received last week, the Superintendent, Dr. Robin Ryan, and law enforcement thought it best to increase patrols in order to ease concerns or apprehension of students, parents or even the staff.

“These threats diverted valuable time and resources for both the police departments and GCISD. We remain steadfast in our joint partnership and commitment to the safety of our students and staff and we will not take lightly any threats against the school district,” said Dr. Ryan.

Federal officials said someone out-of-state called in the threats and there is an investigation going on as they try to track down the person or persons responsible.

In addition to the beefed up police presence, school counselors are available to any student having trouble adjusting to coming back in class after last week’s lockdown.