JEFFERSON CITY, Mo. (AP) — The Missouri Department of Natural Resources says crews are still working to clean up and identify the cause of an oil pipeline leak in suburban St. Louis.

Agency spokesman Brian Quinn said contractors for the pipeline company, TransCanada Corp., were assessing an excavated segment of the Keystone pipeline Wednesday to pinpoint the problem.

The leak was discovered last week near St. Charles.

The department estimates the leak at about 43 barrels, or 1,800 gallons (6,800 liters). It says oil didn’t reach any waterway.

Quinn says about 31 barrels of oil have been collected, and crews have removed more than 1,000 cubic yards of soil.

The department is working to identify nearby wells for groundwater testing.

A TransCanada spokesman says the pipeline remains closed from Steele City, Nebraska, to Patoka, Illinois.