A 34-year-old man was arrested after driving a pickup through a U.S. Coast Guard station gate Sunday morning in western Michigan following a telephoned bomb threat.

The man, whose name was not released, also assaulted Coast Guard personnel at the station before they subdued him, said Jeff Hawke, Grand Haven Public Safety director.

"The suspect is not from Grand Haven," Hawke told reporters. "We're unsure, unclear on whether he is acting alone or not. The investigation is rapidly expanding into other areas of Michigan. No indication of a motive at this time. That part of the investigation is still ongoing."

Emergency dispatchers for Ottawa County notified the Coast Guard Sector Lake Michigan command center in Milwaukee shortly after 6 a.m. "that they had received a telephone call from an unknown man claiming he had a bomb in his truck and was going to blow up Station Grand Haven," the Coast Guard said in a release.

About 6:07 a.m. as notifications for evacuation at the Grand Haven facility were going out, a 4-door Dodge Ram pickup crashed through a gate at the station, about 30 miles northwest of Grand Rapids.

The driver then broke into a building where he attacked workers inside and told them a bomb was in the truck.

No injuries were reported and no bomb was found.

Hawke had said the incident was being treated as "an act of domestic terrorism" because it occurred at a federal building, but that the investigation has not revealed any terror link.

Sheriff's officials in Oceana County said Sunday that the man being held in the Grand Haven case also is the last known occupant of a house that caught fire about 4 a.m. about 45 miles north in Golden Township.