Last year, Houston pipeline company Enterprise Products Partners LP became the envy of the oil industry by finding a loophole in the federal ban on exporting U.S.-produced oil.

But now other oil companies, including BP plc, have complained to regulators that Enterprise is trying to prevent others from cashing in on the lucrative export market.

The Wall Street Journal reports that the U.S. Federal Trade Commission is investigating.

With the price of oil falling into the $40-plus range per barrel, U.S. producers want to ship to overseas buyers willing to pay more.

More information on The Wall Street Journal.