Suffolk County police said Tuesday they have increased patrols around West Islip High School after a third "threat of violence" made against the school in a week.
The district said in a posting on its website that police were once again called to the high school Monday to investigate a threat made on a social media site.
"Activities continued, but doors were locked and security was posted around the building," according to the posting.
The district said no further information is being released, "as this is an active police investigation."
A police spokeswoman Tuesday confirmed the latest threat and said the department continues to maintain increased patrols by both marked and unmarked units in response to the threats.
A canine unit was used in a search last Thursday, after a threat on a social media website, police and school officials said.
The threat was reported in a 911 call at 2:34 p.m. and led to the high school building being placed on lockdown status, the district said.
The search failed to produce evidence of a threat, the district said, and "due to a vague reference to the middle schools," other buildings were searched but no threat was uncovered.
Police confirmed the building searches and said there were extra patrols in the area Friday.
A week ago Monday, police said the high school was the target of a threat of a bombing and a shooting that was found to not be credible.