** Shares of U.S. natural gas companies rise, tracking an increase in natgas futures NGA
** U.S. natgas futures NGc1 up 15.2% at $6.075 per million British thermal units
** Natgas prices soared to three-year high on Monday after an Arctic blast at the weekend froze oil and gas wells and pipes, cutting gas production to a two-year low on Sunday
** Natgas companies: CNX Resources CNX.N up 1.4%, Expand Energy EXE.O up ~1%
** Natgas ETFs: United States Natural Gas Fund UNG.P rises 3% and ProShares Ultra Bloomberg Natural Gas BOIL.P advances 6.3%
(Reporting by Dharna Bafna)
((Dharna.bafna@thomsonreuters.com))