* Futures: Dow up 26 pts, S&P flat, Nasdaq up 1.25 pts (Recasts after reports of explosion)
Dec 11 (Reuters) - U.S. stock index futures fell back after initial gains on Monday, hit by reports of an explosion in New York's busy Port Authority commuter hub.
Police confirmed one person is in custody but were not yet identifying the device used. Local news channel WABC cited police sources as saying a possible pipe bomb detonated in a passageway below ground at Port Authority.
The CBOE Volatility index, a widely followed measure of market anxiety, rose above 10 points.
After rising initially, futures pointed to Wall Street's main indexes opening flat.
At 8:26 a.m. ET (1326 GMT), Dow e-minis were up 26 points, or 0.11 percent, with 14,177 contracts changing hands.
S&P 500 e-minis were unchanged, with 225,353 contracts traded.
Nasdaq 100 e-minis were up 1.25 points, or 0.02 percent, on volume of 18,670 contracts.
(Reporting by Sruthi Shankar and Rama Venkat Raman in Bengaluru; Editing by Arun Koyyur)