* Methane leak occurred in remote swamp area
* Transco system major provider of gas to Northeast
NEW YORK, May 13 (Reuters) - Williams Cos Inc's Transcontinental Gas Pipeline Co LLC (Transco) on Monday said it was investigating a small leak on its Southeast Louisiana Lateral natural gas pipeline in Terrebonne Parish Louisiana and would be conducting unplanned maintenance to repair it.
Gas at the Ship Shoal 28 D would not be available for flow to the Transco system until further notice, a website posting said.
A spokesman said the company had isolated the 16-inch (40-cm) line after a methane leak was discovered during a normal pipeline patrol. The incident occurred in an unpopulated, swamp area near Mosquito Bay, Louisiana.
There were no injuries or third-party damage.
One producer was affected by the shut-in of a very small amount of gas, the spokesman said. There was no estimate on the length of repairs.
Transco is a major provider of natural gas to the U.S. Northeast. Its more than 10,000-mile (16,000-km) system has the capacity to carry 9.7 billion cubic feet of supply per day from the Gulf Coast to New York City.
Gas on the Transco system at the New York citygate was one of the biggest gainers in the cash gas market on Monday, rising 10 cents to $4.12 per million British thermal units. Traders said the rise was due to cool weather in the Northeast early this week that boosted late-season heating demand and not due to the leak.
The spokesman confirmed that delivery points north of the incident had not been affected.