Royal Dutch Shell PLC (NYSE:RDS.A) shut down a major crude oil pipeline in Nigeria for the second time in a month, the Anglo-Dutch energy giant said Friday.

The company shut down the 24-inch Trans Niger Pipeline as a result of what the company says is a confirmed leak caused by thieves, according to AFP. The previous shutdown was for the same reason.

Shell said that the illegal oil theft totaled about 150,000 barrels per day, but the company did not disclose how many days the oil had been leaking.

Theft and disruptions in oil supplies occur frequently in Nigeria. Pipeline vandalism increased by 224 percent from 2010 to 2011, according to the U.S. Energy Information Administratio, or EIA.

In April 2012 about 400,000 barrels per day of oil were stolen, leading to a 17 percent drop in oil sales, according to Nigeria’s Ministry of Finance.

Shell is Nigeria's largest oil producer, and it was estimated in 2012 that 6 percent of the country's total production on average was lost to oil theft and spills.

According to the EIA, criminals use small boats to navigate swampy shallow waters of the Niger Delta where they puncture pipelines to tap the oil and then pour it into small tanks.