This story has been updated.
CORTLANDT, N.Y. -- A lockdown was lifted at Hendrick Hudson High School and Frank G. Lindsey Elementary School Tuesday at approximately 3:15 p.m.
The lockdown was put in place after threatening phone call and an incident of vandalism, Superintendent Joseph Hochreiter said in a posting on the school's Facebook page.
Students were dismissed shortly after the lockdown ended, Hochreiter said. State police and other agencies assisted in conducting a thorough sweep of the school and deemed it same for dismissal, said Hochreiter.
"This is an ongoing investigation and we appreciate your support and understanding," Hochreiter said. "We will share relevant information with you once the investigation is complete and finalized."
Hochreiter praised staff and students for their professionalism during the lockdown.
"The administration and staff executed our safety protocols with precision," Hochreiter said. "Their planning paid great dividends. We take these threats very seriously and will continue to partner with the appropriate agencies to keep our students safe."
Hochreiter asked parents to use this incident as an opportunity to speak to their children about the severity of these threats and the ripple-effect it has throughout our entire school community.
State police are investigating a threatening phone call the high school main office received at 1 p.m.
Frank G. Lindsey was locked down due to its proximity to the high school, Hochreiter said.
Click here to sign up for Daily Voice's free daily emails and news alerts.