Shell said oil seen off the coast of Nigeria isn\'t likely from a spill last week but its investigators were working to assess the potential impact. Shell last week announced that it closed operations at its offshore Bonga production platform following the discovery of a leak from an export line. The company said preliminary estimates indicate less than 40,000 barrels of oil spilled. The leak, the company said, came during routine operations to transfer oil from an offshore production platform to an oil tanker. Shell has a legacy of oil spills in the Niger Delta region. The company blames saboteurs and oil bandits for most of the incidents. The company said it observed oil in the region that it believes came from an unidentified third party. Oil from that spill, the company said, has come onshore. Shell Nigeria Chairman Mutiu Sunmonu said oil reaching shore likely isn\'t from the Bonga spill. Most of that, the company said last week, dispersed naturally. \"All necessary measures will be taken to protect the coastline, wildlife and the communities that live there, and where necessary to clean onshore areas,\" he said in a statement. \"We do not believe that any of the oil from Bonga has reached the shore.\" The Bonga deep-water facility is about 75 miles off the Nigerian coast and could produce as much as 200,000 barrels per day.