VANDERGRIFT — Guards from the federal Department of Homeland Security are patrolling a former nuclear waste dump as officials rethink their cleanup plans after finding what they called more “complex” nuclear material than expected.

Neither the Army Corps of Engineers, which is managing the cleanup, nor the Nuclear Regulatory Commission would say exactly what material was found at the Armstrong County site.

Scott McConnell, spokesman for the National Protection and Programs Directorate, which is part of the Department of Homeland Security, said the elevated security measures were put in place at the Corps’ request and were not related to any specific threat in the area. He said the measures result from “an abundance of caution.”

Guards from the Federal Protective Service, part of the homeland security department, have been posted for about a year.

The dump along Route 66 was used to store nuclear and chemical waste from the former Nuclear Materials and Equipment Corp. in Apollo and Parks townships from about 1960 to the early 1970s. The cleanup was commissioned under the Formerly Utilized Sites Remedial Action Program.