Consumer rights group Which? has welcomed the investigation announced by Ofgem into the UK's energy market.
"a watershed moment for the broken energy market and millions of people struggling to cope with spiralling bills" says Which?.
The investigation must leave no stone unturned in establishing the truth behind energy prices - says Which? @whichcampaigns
More top news
Coal's share of the power mix had fallen to 7%, while wind climbed to new highs to provide 15% of the country's electricity.
State Department spokeswoman Heather Nauert said Pence "was ready to take this opportunity."
Opposition activists said government forces have brought in more reinforcements in recent days.