The U.S. Environmental Protection Agency is concerned that permitting for the southern segment of the proposed Keystone XL pipeline could be insufficient and has asked for a more extensive review.
An official in the EPA's region that oversees Texas wrote a letter to the Army Corps of Engineers saying 61 water crossings near Galveston are too large for the broad permits being pursued. The official wants an environmental review that includes a public comment period.
The letter, written in November, was released Thursday.
The corps says it's reviewing TransCanada's permit request.
This is the latest obstacle for a controversial pipeline project that has created tensions between the U.S. and Canada.
The pipeline is designed to transport Canadian crude oil across the Midwest to Texas Gulf Coast refineries.