WASHINGTON (AP) — Tech-savvy students and others are using smartphone apps, social media and Internet phone services to make anonymous reports of bombs and other threats of violence at schools. The result: school evacuations and police sweeps.

In most cases, such a threat turns out to be a hoax. Still, the use of the modern technologies has made it that much harder to determine if a threat is real and to find the culprit, compared to the past when they were often called in by pay phone or written on bathroom walls.

Just this week, a 16-year-old from Gateway High School in Kissimmee, Florida, was arrested for posting about a bomb threat on Twitter because “she was angry and did not want to go to school,” according to the Osceola County Sheriff’s Office.

School safety experts say the number of such incidents appears to be increasing — as are the complexity of the cases. The latest figures from the National Center for Education Statistics for the 2009-2010 school year show 5,700 such disruptions.

“They send a great deal of fear and panic throughout a community,” said Kenneth Trump, a school safety consultant who is president of National School Safety and Security Services. His group reviewed more than 800 threats reported in the media during the first half of the 2014-2015 school year and found that about one-third were sent electronically using text message, social media, email or other online means.

Complicating matters, the threats aren’t just coming from within school walls or even a school’s neighborhood.

Last fall, Lakota Middle School in Federal Way, Washington, was placed in lockdown and police responded after an email purportedly from the Islamic State group demanded ransom money and threatened to “shoot and kill” every American, according to a police report. A 14-year-old student was arrested after admitting the email had been sent by her online friend “Ryan” after she told him to “swat” her school because she thought it would be funny, police said.

“Swatting” plays off the idea of issuing a threat that draws a SWAT team in response, disrupting activities at the target of the threat. It appears to have originated with pranksters in the online gaming community.

In a separate case, a 14-year-old in western Michigan was ordered by a judge to pay nearly $8,000 in restitution to the Coopersville Area Public Schools and the Ottawa County Sheriff’s Office for his involvement in a swatting incident that put schools in lockdown after a caller using computer-based technology made threats against the schools. Authorities say the call was made by a person code-named “Ransom,” whom the teen had met online. “Ransom” is believed to live in the United Kingdom and is suspected in a string of similar incidents from coast to coast, authorities said.

“He will learn from this,” the teen’s father said, according to the Grand Rapids Press in Michigan.

The motivations of the threat makers vary: avoiding a test, revenge or simply to show off. With swatting, a motivation appears to be thrill-seeking, said Capt. Mark Bennett with the Ottawa County Sheriff’s Office.

It’s not too difficult for students to figure out how to pull off such an incident, said Justin Cappos, a computer science professor at New York University who studies cybersecurity. “You wander to the wrong parts of the Internet and you can learn how to do it and not get caught,” Cappos said.

With each incident, there’s a risk when authorities respond, said Detective Jerrad Ely, a digital forensics expert with the Mount Vernon Police Department in Washington who has been investigating a bomb threat case against a school in his community. “They could inadvertently get hurt when police are just trying to do their jobs based on the best information that they have,” he said.

Applications such as Burnbook, Afterschool, Yik Yak, Whisper and Kik also have been used by students to make threats anonymously.

In Michigan, Superintendent Timothy Stein of the Flushing Community Schools wrote to parents in December informing them about a posting on Afterschool that said, “Bringing a Gun to School.” The posting had been brought to the high school principal’s attention by a text message; police quickly determined that it was not a credible threat.

“I encourage you to ask you child to stop using this app and remove it from their phone,” Stein said.

Every threat has to be taken seriously even though in most cases the called-in danger is not real, said David Pennington, superintendent of schools in Ponca City, Oklahoma, and president of the AASA School Superintendents Association.

Meanwhile, social media and other electronic means of communication are keeping parents informed about threats. Mindful of past school shootings, they are demanding that children be pulled out of school even as school and law enforcement officials investigate.

“The security of people has been greatly eroded in this country, as you know, just through awful things that have happened,” said Mark Davidson, deputy superintendent at the Federal Way Public Schools.

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Follow Kimberly Hefling on Twitter: http://twitter.com/khefling