Updated 9:50 a.m. Dec. 20:

The Greenfield Police Department had an increased presence at Greenfield High School and Whitnall High School on Thursday, and will again Friday, after officers investigated rumors of possible violence occurring at the schools Friday.

According to Assistant Chief Paul Schlecht, a thorough investigation conducted with the assistance of the high schools' administrators revealed no credible threat at either school.

This issue, Schlecht said, appears to be along the same lines as threats investigated by other southeastern Wisconsin schools and police departments regarding the end of the Mayan calendar and the end of the world.

The threats come just five days after the Sandy Hook Elementary School shooting in Newtown, Conn.

Schlecht said the police department will continue to take every threat seriously and investigate them thoroughly.