IndyCar driver Justin Wilson blamed a faulty transmission for causing an accident in pit lane that sent two crew members to hospital during the Honda Indy Toronto's first practice session on Friday.

Sebastien Bourdais' pit crew member Chuck Homan sustained the most severe injury after he had his leg pinned between two cars. Raffi Aroyan, also a member of Bourdais' Dragon Racing team, was also taken to hospital with an ankle injury.

The crash happened in the pits, when Wilson had difficulty stopping his car and ran into the back of Bourdais' parked car.

In a statement posted on his website, Wilson said he was stuck in first gear and couldn't get it into neutral. Compounding the problem, Wilson said, was the car's brakes were cold making it even more difficult for him to stop.

"At the last second I tried to dive into the wall to take the speed off, but those guys were there and had no idea I was coming," Wilson said. "I really hope they are OK."

Two others were hurt in the accident and were treated and released from the infield care center. They were Dragon Racing's David Martin and Michael Cole, a member of Wilson's Dale Coyne Racing team.

Wilson returned to practice after the transmission problem was diagnosed, but his session ended quickly. Wilson was forced to put his car into the wall to avoid hitting Alex Tagliani, who had spun out in front of him in Turn 8.

"It was just a horrible session," Wilson said. "We'll have to regroup and hopefully get back out for the next session."

Wilson won at Texas last month and ranks 11th in the points standings.

Qualifying in Toronto takes place Saturday. The race is Sunday.