The increased police presence is "out of an abundance of caution," according to the statement from Lt. Kraig Gray, the department's public information officer.
On Monday night, Greenwich High School received an anonymous online comment that was nonspecific and may be interpreted as a threat, he said.
"We are comfortable that the school is safe and secure, and it is our understanding that the normal routine of the school will be followed," Gray said.
No further information was released by police.
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