HAVERHILL — Police said an extensive search Wednesday of the area around Haverhill High School failed to turn up a gun they believe a student attending summer school brought into the building last week.

The student was seen carrying a gun at school, according to police. He fled the building and later was arrested, but officers did not find a gun in his possession.

"Although we feel there is no danger to the public, citizens are cautioned if any weapon is found to report it to the police immediately," police wrote in a Facebook post late Wednesday afternoon.

"The Haverhill Police Department would like to thank the Massachusetts State Police SERT Team, for their assistance in an extensive area search around Haverhill High School, Route 97, and Monument Street," the posting reads. "This search was conducted as a result of the July 29 incident at Haverhill High School. No firearm was located as a result of the search." 

Several police cruisers and officers were at Haverhill High School on Wednesday morning, but school officials said there was no need for students or school staff to be concerned. 

Haverhill High Principal Glenn Burns used the school intercom Wednesday morning to read a message from School Superintendent Margaret Marotta to students and staff.

Burns told The Eagle-Tribune that people who were at the high school included students with special needs who are in an extended school year program, along with program staff, and a small group of math teachers who were participating in professional development.

The message said police officers were at the school not due to an emergency or any threat to the school, but to follow up on an incident that happened last week on the property.

"There will be an increased police presence this morning in the area surrounding Haverhill High School,'' Marotta's message stated. "This is in follow-up to the previous incident last week, as police continue their thorough search of the area.''

Burns said he did not have information as to why police conducted the search Wednesday and that any new information surrounding the investigation will be coming from the superintendent's office and police.

Police are continuing their search for the gun.

Burns said Wednesday morning that police were conducting a "grid search'' of the area. The search was  to include the school property and nearby property.

Several state police cruisers were at the school. Local officers were also present.

Marotta said she scheduled ALICE training — training for active shooter response — for teachers at all city schools, and that the training will take place the day before the start of school.

Burns said he expects the training will help ease any tensions or anxieties that may exist among staff members in the wake of last week's incident.

"We had already debriefed staff that was here over the summer and there will be some things we address and some things we won't as it's still an ongoing investigation," he said.