You could almost read the exasperation in Pine Lake Middle School Principal Michelle Caponigro’s letter to parents.

Pine Lake Middle School administrators called police to campus Thursday for the second time in as many weeks to investigate a bomb threat found in a boys bathroom as the school day ended. The threat came on the heels of a similar incident Jan. 9 that forced administrators to evacuate the campus.

A student reported finding a message written on the wall in a boys bathroom in the eighth-grade hall.

“Our hunch is that this is a prank,” Caponigro wrote. “But exercising reasonable caution, we have called 911.”

Police swept the campus to search for explosives, once again finding nothing.

According to King County Sheriff spokeswoman DB Gates in response to questions from The Reporter, the cost to law enforcement resources for Thursday’s sweep was minimal. But that cost rises when police dispatch explosive detecting dogs and additional officers to a threat that proves not to be credible — and not just in terms of dollars and cents.

“Anytime we have to respond to and investigate any call that turns out not to be true, is made up, or otherwise not a police issue it takes away from any other citizen calling us for assistance,” Gates said.

Gates said she had “no idea” why a student might leave a false threat on campus.

“If we could figure that out we could potentially put an end to the false threats,” she said. “This is not a new phenomenon though. In my high school years … we had bomb threats called into our school which normally resulted in us being dismissed for the day. Now the schools and public need to look at them a bit differently in light (of) incidents of school shooting.

“And the media plays into it. There is a whole doctoral dissertation that could be done studying whether the increased reporting causes copycats or not.”

But students who find a threat should not be discouraged from reporting it to authorities, Pine Lake’s principal said. In a second letter written after police cleared the scene, Caponigro praised the student who reported the threat.

“He did the right thing and we will always take what students report to us seriously,” Caponigro wrote. “We continue our investigation and certainly hope to identify the individual responsible.”

She urged parents to talk to their children and share any information on the matter at caponigrom@issaquah.wednet.edu or deletism@issaquah.wednet.edu.

After-school sports and activities were not canceled and school was set to resume normally Friday morning.