No oil is leaking from the sunken Deepwater Horizon drilling rig or pipe around the vessel, its owner Transocean said on Wednesday.

A two-day underwater investigation by Transocean and the U.S. Coast Guard confirmed that no oil is leaking from the Deepwater Horizon, which sank in April 2010 in the Gulf of Mexico after BP Plc's Macondo well blew out and caused the world's worst marine oil spill.

On September 27, there were sightings of an oil sheen near the capped well.

Fracking, the latest craze in the quest to produce oil and gas, has been blamed for environmental problems ranging from flammable tap water to minor earthquakes. Now a new risk is emerging: sand mining.

To squeeze hydrocarbons out of shale through hydraulic fracturing of the rock -- the process known as fracking -- producers need to pump an enormous amount of sand and other materials into the ground.

Obtaining the sand for this requires removing the top layer of earth over a sandstone deposit and using heavy equipment and large amounts of water to produce the fine grains.

The danger of more oil leaking from Exxon Mobil Corp's ruptured pipeline in Montana has ended, the Environmental Protection Agency said.

The Silvertip pipeline burst on July 1, spilling an estimated 42,000 gallons of oil, or 1,000 barrels, into the scenic Yellowstone River.

Exxon has now drained the two segments of pipeline that were on either side of the break.

Exxon Mobil said it had begun preliminary work to replace the pipeline that ruptured and spilled an estimated 1,000 barrels of oil into the Yellowstone River in Montana two weeks ago.

Exxon, the world's largest publicly traded oil company, said it was aiming to meet federal requirements on corrective action around the Silvertip pipeline before resuming operations.

Preliminary work includes t

Exxon Mobil Corp defended hydraulic fracturing at its annual shareholder meeting on Wednesday, even as investors peppered CEO Rex Tillerson with concerns and questions about the technology.

A shareholder proposal requiring greater disclosure by Exxon on the risks and impact of its hydraulic fracturing practices was voted down by about 70 percent of the world's largest publicly traded oil compan