Hundreds of angry longshoremen stormed through a grain shipping terminal in Longview, Wash., early Thursday and held security guards at bay while descending on a disputed train full of grain, cutting brake lines and dumping cargo.

The predawn labor protests came after a clash with police Wednesday in which hundreds of longshoremen blocked railroad tracks near Vancouver, Wash., to prevent grain cargo from reaching an export terminal 45 miles farther west. In that protest, they far outnumbered officers, pelting police with rocks and spraying them with pepper spray, police said.