Elgin Independent School District students were placed under lockdown Monday after police alerted the district to a possible threat involving its high school campuses. The district lifted the lockdown and resumed classes after authorities determined the threat was not credible. Police notified Elgin ISD at about 12:40 p.m., Superintendent Christopher Bailey said in a statement. The district received the all-clear at about 2:20 p.m., roughly 100 minutes later. The district did not provide details about the nature of the reported threat or identify the high school campuses involved.