James Hinchcliffe is "awake and communicating" according to his long-time girlfriend Kirsten Dee, who is with the 28-year-old driver at IU Health Methodist Hospital where he is recovering from a high-speed practice crash at Indianapolis Motor Speedway on Monday.

Dee posted the comments on her Facebook page, adding that Hinchcliffe was "doing amazingly" and also thanking fans for their support and well wishes.

In an official medical update from the Verizon IndyCar Series, Hinchcliffe is now reported to be in stable condition following surgery for an injury to his pelvic area and upper left thigh.

He is undergoing further evaluations in the Intensive Care Unit and has been ruled out of Verizon IndyCar Series competition for the foreseeable future, the update added.

"He's stable and improving," said Dr Timothy Pohlman, senior staff trauma surgeon at the hospital. "His condition was critical upon his arrival and I think the IndyCar system as a whole needs to be commended for how well they can take care of drivers in this situation."

Hinchcliffe's #5 Schmidt Peterson Motorsports Honda suffered a suspension failure and crashed at almost full speed in turn 3 of the two-and-a-half-mile oval during practice for next Sunday's 99th running of the Indianapolis 500. The car suffered extensive right-side damage and a brief fire as broken oil lines ignited, almost turning over before righting itself as it slid to a halt.

The Holmatro safety team was on the scene in seconds, and according to media reports on Tuesday it was their prompt action in extracting the driver from the cockpit and treating heavy blood loss from the leg wound that was largely responsible for avoiding a far worse outcome for Hinchcliffe.

"Words can't describe how thankful I am to the Holmatro Safety Team," Hinchcliffe is quoted as saying in the latest medical update released on Tuesday. "Those guys, in addition to the doctors and staff at the hospital, are my heroes.

"I can't say enough how much I appreciate the outpouring of support from IndyCar fans, my family and fellow drivers. We are all one big family and it feels like that today."

IndyCar said that additional updates to Hinchcliffe's condition will be released when available.

"Obviously, we're relieved that James is awake and out of surgery," Schmidt Peterson Motorsports team co-owner Sam Schmidt was reported as saying on Monday night. "That's the most important thing on our minds right now and we will do absolutely everything required to ensure a complete recovery."

As well as the quick response by the safety team, the proximity of the hospital to the speedway was also said to be important in Monday's trauma situation, as the ambulance was able to travel there directly without needing to go to the in-field care centre and use the medical helicopter to transport him which would have been the case at many racing venues.

On Tuesday, Sam Schmidt confirmed to The Indianapolis Star that a piece of the front right suspension had pierced the driver safety cell monocoque and penetrated Hinchcliffe's thigh, fixing him in the car and making rapid extraction all the more difficult for the safety team.

Although the suspension part didn't break any bones, there was soft tissue damage and a severed major artery in Hinchcliffe's leg which led to the profuse bleeding, which if it had not been treated immediately could have been life-threatening.

According to media reports, the wishbone that did the damage to Hinchcliffe's thigh was among the suspension parts that had recently needed to be strengthened in order to cope with the increased downforce effects of the new aero kits that were introduced at the start of the 2015 season.

"Previously, it would have folded," said Schmidt, who described the piece as having cut through Hinchcliffe "like a knife".

Schmidt indicated that the team - which also includes drivers James Jakes and Conor Daly - still intends to compete in Sunday's race. While Hinchcliffe's race car was destroyed in the accident, a backup could still line-up on the starting grid if a replacement driver can be signed up in time. Schmidt said that the team was considering five candidates for the seat.

"I'm sorry about what happened to Hinch," said former Indy 500 champion Tony Kanaan. "The accident was a mechanical failure and completely unrelated to anything else that's happened here this last week."

"That was a bad accident, we're still just thinking about Hinch and hoping he's okay," said Ed Carpenter, who escaped unhurt from his own big accident at the Speedway on Sunday.

"Incidents are going to happen here in IndyCar," pointed out Carpenter's team mate, Josef Newgarden. "With any high-speed motorsport, it's going to happen. They're very safe cars, though. You think about the people that do walk away from big hits like that and I think Dallara and IndyCar do as best a job as they can. They are always trying to improve safety and continuing to make it better. You're going to have those crashes and things that come up, but your job is to get back in the car and make the most of it."

"Really wishing a speedy recovery for Hinch, all of us are wishing that," added former F1 driver Takuma Sato, now driving with AJ Foyt Racing.

"As a driver, a crash like James had is just something you never want to see. I hope he makes a quick recovery," contributed Graham Rahal.

Hinchcliffe had qualified in 24th place for the Indy 500. He is in his first season with SPM after moving from Andretti Autosport over the off-season. The 28-year-old won the inaugural Indy Grand Prix of Louisiana on April 12 and also finished seventh in the Honda Indy Grand Prix of Alabama at Barber Motorsports Park on April 26.)

In 73 starts covering five Verizon IndyCar Series seasons, Hinchcliffe has four victories and 19 top-five finishes. In four Indianapolis 500 starts, he has a best finish of sixth in 2012 and started the race from second place in 2014.