The SpaceX rocket that exploded on the launch pad at Cape Canaveral also blew up a pricey Facebook satellite it was supposed to deliver into orbit, leaving social network company boss Mark Zuckerberg "deeply disappointed."

The four-minute-long explosion occurred as the 604-ton Falcon 9 rocket was being fuelled with a powerful mixture of liquid oxygen and rocket-grade kerosene propellant for test firing before its weekend launch.

The cause of the blast is still unknown and is being investigated, according to a tweet by SpaceX CEO Elon Musk. He described it as a "fast fire, not an explosion."

No one was injured in the blast, which SpaceX referred to as an "anomaly."

The rocket's payload was a $200m (£151m) satellite — called Amos 6 and owned by Israeli company Space Communications or Spacecom — to be used by Facebook to bring Internet access to remote villages in Africa, the Middle East and Europe. The operation also involved French satellite firm Eutelsat Communications.

"I'm deeply disappointed to hear that SpaceX's launch failure destroyed our satellite," Zuckerberg wrote in a post while traveling in Africa. He noted that the satellite "would have provided connectivity to so many entrepreneurs and everyone else across the continent".

Zuckerberg said other technologies are in the works to boost Internet access, adding: "We will keep working until everyone has the opportunities this satellite would have provided." Facebook already completed its first successful experimental flight in June of Aquila, an unmanned, solar-powered plane that will also be used to beam the Internet into remote areas.

Launch Complex 40, where the blast occurred, is an Air Force facility which has been leased to SpaceX, reported CNNMoney. The company has launched 25 rockets from the site since 2010.

Nasa's facilities at Cape Canaveral were not damaged by the blast and none of the planned Nasa flights have been affected.

"Today's SpaceX incident — while not a Nasa launch — reminds us that spaceflight is challenging," Nasa tweeted. "Our partners learn from each success and setback."

The fallout for Musk and Zuckerberg remains to be seen and industry analysts believe the explosion will likely delay space launches.

"It's clear there will be some sort of delay," Phil Smith, senior space analyst at the Tauri Group, told the Los Angeles Times.

The blast — the second Falcon 9 failure in 14 months — could also be a setback to Musk's efforts to prove that his company can safely launch and reuse rockets. SpaceX just announced that it had signed its first customer to launch a satellite with a reused booster.

And it recently landed its first big Pentagon job — an $83m (£63m) contract from the Air Force to launch a global positioning system satellite in 2018.

The blast came just as Musk was also set to announce Tesla Autopilot improvements in the wake of a fatal crash in Florida in May. He is now delaying that announcement. Meanwhile, he is also trying to finance a $2.4bn (£1.8bn) deal for Tesla to acquire SolarCity.

Tesla shares fell 5.3% Thursday to $200.11 (£150.79).

As for Facebook, it was the first attempt by the company's initiative to deliver Internet signals from space. The Amos 6 was a total loss.

The satellite's manufacturer, Israel Aerospace Industries, took out an insurance policy on the Amos 6 worth its total cost, a source told the Times. It is estimated to be worth at least $200m (£151m), while the cost of launching and operating it for a year is believed to be $85m (£64m).

But the policy covers transit and pre-launch processing of the satellite from the factory to the launch site. Spacecom's insurance policy does not cover risk of loss until the actual launch.