The CEO of Enbridge Inc. says he is "deeply saddened" by the death of a woman in central Kentucky in an explosion on Thursday involving the company's Texas Eastern natural gas pipeline.

Al Monaco promised that the line will not go back into service until it is "absolutely safe to do so," noting that the Calgary-based company has a team on site working with members of the U.S. National Transportation Safety Board to discover the cause.

"Our hearts go out to the community and the family," said Monaco on a conference call.

The pipeline rupture caused a massive explosion that killed one person, hospitalized five others, destroyed railroad tracks and forced the evacuation of a nearby mobile home park, authorities said.

Kentucky State Police said at least five homes were completely destroyed and structures within 457 metres had damage. He said a handful of people who were missing after the blast have now been accounted for.

Enbridge spokesman Jim McGuffey said two other nearby gas lines don't appear to be affected but will be inspected. He said there's no indication of what might have caused the explosion.

In this photo provided by Naomi Hayes, a fire burns after an explosion near Junction City, Ky. A regional gas pipeline ruptured early Thursday, causing a massive explosion. (Naomi Hayes via The Associated Press)

Also Friday, Enbridge announced the beginning of an open season on its Canadian Mainline pipeline system, with bids to be accepted until Oct. 2.

The company wants to change from a common carrier model, where all of the system's capacity is available on a month-to-month basis, to one where shippers can lock into contracts of up to 20 years, starting on July 1, 2021.

Mainline capacity would be 3.225 million barrels per day, assuming the delayed Line 3 replacement project is completed, of which up to 2.9 million bpd would be contracted and 10 per cent, or 325,000 bpd, remaining in spot service.

The change is subject to regulatory approval.

Earnings up

Enbridge says a number of unusual factors boosted its second-quarter profit to $1.74 billion, while operations also performed well amid strong demand for transporting crude oil through its pipeline systems.

Net income attributable to common shares of the Calgary-based company was 86 cents per share.

That was up from $1.07 billion or 63 cents per share in last year's second-quarter, which also included unusual items — one time gains, losses or expenses that are not considered part of normal business operations.

Enbridge's adjusted earnings and revenue were also up, beating analysts' expectations.

Adjusted earnings rose to $1.35 billion or 67 cents per share, from $1.09 billion or 65 cents per share, while revenue was $13.26 billion, up from $10.74 billion.

Analysts had estimated $11.06 billion of revenue and 59 cents per share of adjusted income, according to financial markets data firm Refinitiv.