An Oklahoma man accused of attaching a homemade bomb to a natural gas pipeline has pleaded not guilty.

Forty-year-old Daniel Herriman entered the plea Tuesday before Magistrate Judge Kimberly West in U.S. District Court in Muskogee.

The FBI says Herriman was arrested Friday after calling 911 and telling the Seminole County Sheriff's Office he had planted a bomb on the pipeline and wanted to surrender.

The FBI alleges Herriman admitted making the device and placing it on the pipeline Aug. 7 with a timer set to detonate at 2 a.m. The device did not explode and there was no damage. FBI spokesman Clay Simmonds said the agency doesn't know of a motive.

The bomb was discovered Wednesday at the Enerfin Resources substation near Okemah in Okfuskee County.