Jack Harvey was taken to a hospital and Helio Castroneves needed an ice pack and X-rays. A pair of cars went airborne, the leaders crashed each other and the entire Andretti Autosport fleet was eliminated.

Indianapolis 500 winner Marcus Ericsson, meanwhile, won the IndyCar season-opening race.

Ericsson outlasted the carnage on the downtown streets of St. Petersburg for a surprise victory for Chip Ganassi Racing on a swampy Sunday in Florida. It was the fourth career IndyCar victory for the Swedish former Formula One driver.

"I think people forget us in some conversations when they talk about the championship," Ericsson said. "We're here to win. We won the 500. We were leading the championship for a long time. We're here to win."

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It was supposed to be an Andretti car in victory lane, at least based on the speed the team showed all weekend. Romain Grosjean and Colton Herta started on the front row, but things began to unravel right at the start.

A seven-car accident on the very first lap knocked five cars out of the race, including Andretti driver Devlin DeFrancesco, who was sent airborne when rookie Ben Pedersen slammed directly into his stopped car. Castroneves, a four-time Indianapolis 500 winner, limped away from the crash while his Meyer Shank Racing teammate Simon Pagenaud clutched his hand.

Castroneves left IndyCar's new mobile medical care center with an ice pack on his right hand, and a clean X-ray taken on his right knee. Pagenaud said his finger was bruised but he was fine.

Harvey wasn't so lucky and was briefly seen at a local hospital after Kyle Kirkwood became the second Andretti driver to go airborne and sailed directly over Harvey's head. Rinus VeeKay had slid into a tire barrier, Harvey ran into the back of VeeKay and Kirkwood launched over both cars.

"It was a pretty disappointing way for our race to go there," Harvey said later through his team, Rahal Letterman Lanigan. "I really couldn’t avoid Rinus and then just had a little bit of pain in both wrists when I was trying to get out of the car. Physically, I’d say it was a tough race but I felt great."

When Kirkwood launched, Michael Andretti slammed his hand on the pit stand in disgust.

INDYCAR DRIVER DEVLIN DEFRANCESCO GOES AIRBORNE IN SCARY CRASH DURING FIRST RACE OF SEASON

But there was more to come.

Herta was sent into a tire barrier by contact from reigning IndyCar champion Will Power, who received an avoidable contact penalty, to leave Grosjean as the last remaining chance for Andretti.

But as Grosjean and defending race winner Scott McLaughlin raced side by side for position, the two cars touched in what appeared to be a game of chicken headed into a corner. Neither driver lifted and both cars slammed into a tire barrier.

Grosjean was furious, first throwing his arms up in disgust and then pounding his first on the stack of tires as he screamed. McLaughlin received an avoidable contact penalty. Andretti muttered an expletive and buried his head in his hands.

McLaughlin and Power said they'd seek out Grosjean and Herta, respectively, to apologize, and McLaughlin did go to Grosjean's team truck and hugged him. Scott Dixon, meanwhile, apologized repeatedly for contact with Felix Rosenqvist on the opening lap that set in motion the bigger crash behind them.

Ericsson, meanwhile, passed Pato O’Ward for the win with three laps remaining when O’Ward suffered a brief loss of power. O’Ward pounded his fist in disgust as Ericsson sailed past for the win for Honda.

O'Ward was second in a Chevrolet for McLaren and could barely find any words to speak in his initial disappointment.

"Just very annoying to give it away like that," O'Ward said with a sigh. "The team can't have this happen. We just got 10 points thrown away. We'll have a look at all the data and make sure that doesn't happen."

Ericsson had no problem winning that way.

"That's racing," he said.

Dixon, the six-time IndyCar champion, was third for Ganassi for his 193rd top-five finish, tying him with Mario Andretti for most all-time. Dixon's top-five percentage is 52%.

Alexander Rossi was fourth in his debut race with new team McLaren.

Callum Ilott finished a career-best fifth for Juncos Hollinger Racing and was followed by Graham Rahal of Rahal Letterman Lanigan and then Power of Team Penske. Alex Palou of Ganassi was eighth while RLL driver Christian Lundgaard and David Malukas rounded out the top 10.

Marcus Armstrong, a rookie who moved from F2 in Europe to race for Ganassi in IndyCar this season, finished 11th in his series debut to make Ganassi, and not Andretti, the team of the day.

UP NEXT: IndyCar next races on April 2 at Texas Motor Speedway, where Josef Newgarden is the defending race winner.