On Lap 7 of the 500-mile race, Wickens came alongside Ryan Hunter-Reay in the No. 28 Andretti Honda and subsequently spun after contact.
"I was lucky to get out of that one", said Hunter-Reay, who was the first driver checked and released from the infield medical center.
The 29-year-old was alert when medical workers attended to him before transporting him to the hospital in a helicopter.
After a almost two-hour delay to fix the fencing, the race resumed without another spate of aggressive driving - Graham Rahal tangled with Spencer Pigot as the field was brought to green at the race's start - and ended without another caution.
Alexander Rossi, who won the race, said, "It's tough to really celebrate after what happened". Justin Wilson died from a head injury in 2015 when a piece of debris from a crashed vehicle bounced off the track and hit his helmet.
Sato and Hunter-Reay were quickly released from the medical centre, while Hinchcliffe and Fittipaldi are undergoing checks.
"I took my hands off the wheel when I went backwards, and I think some piece of debris came in as I was holding them [hands] in, kind of just smacked the top of them so I took of bit of beating, but nothing is broken, just some swelling and some cuts", Hinchcliffe continued.
"It's unfortunate but I just hope Robert is okay. He was in Ryan's blind spot so Ryan didn't see him".
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"That's the worst thing you can see. At least he is alive", said French driver Sebastien Bourdais. But because of the speed of the vehicles, Wickens' auto soared into the fence at Pocono Raceway and started spinning in the air repeatedly.
Graham Rahal wrecked Spencer Pigot at the start of the IndyCar race at Pocono Raceway. Pigot spun out and hit the wall. The impact of the wreck tore out about 80 feet of fence, damaged a few posts and stopped the race.
The race was red flagged, and drivers were allowed out of their cars while the fencing was repaired.
But Bourdais, who said the repairs were "pretty lousy" raised his concerns about the quality of the repairs and condition of the fence before he got back in the vehicle. Hinchcliffe headed to the hospital to be with Wickens, who is a close friend and Schmidt Peterson Motorsports teammate.
The IndyCar race at Pocono Raceway remains on hold following a crash that sent driver Robert Wickens to the hospital.
Wickens had reeled off five straight top-five finishes entering Pocono and matched a career-best finish of second in the previous race at Mid-Ohio.
Team owner Roger Penske said it would be tough to field a fifth auto for driver Tony Stewart in next year's Indianapolis 500.