NEW YORK, June 6 (Reuters) - U.S. heating oil futures trading was halted briefly on the electronic trading platform CME Globex Friday after they struck the maximum fluctuation limit of 25 cents, a NYMEX spokeswoman said.

“The trading on heating oil was halted at 1:13 p.m. EDT and resumed some three minutes or so later,” said Anu Aluwahlia, the NYMEX spokeswoman.

NYMEX trading on the floor was not affected, she said.

Traders were confused and some said they did not even know that a trading halt had been imposed.

Current rules on floor trading call for a trading halt for five minutes if a contract hits the fluctuation limit and trades continuously at or above that level for five minutes.

Aluwahlia said that the resumption of heating oil trading after the brief pause called for the doubling of the fluctuation, to 50 cents, which must be hit before another trading halt is called.

Aluwahlia said that NYMEX rules also called for other energy contracts --- crude and RBOB gasoline -- to have their maximum fluctuation doubled after the heating oil hit its maximum.

“The rules call for all those three contracts -- crude, heating oil and gasoline -- to have their maximum fluctuations doubled after any one of them hits the limit,” she said.

The fluctuation limit for crude now stands at $20 and for RBOB gasoline to 50 cents, she said.

At 1:48 p.m. EDT/1748 GMT, NYMEX July heating oil xHON8 traded at $3.9321 a gallon, up 25.13 cents, or 6.82 percent, after trading from $3.68 to $3.9550.

NYMEX heating oil hit a record $4.0153 on May 22. (Reporting by Gene Ramos; Editing by Christian Wiessner)