Felipe Massa says a failure with his DRS mechanism was the cause of his crash in the opening free practice session in Canada and Williams is investigating the cause of the fault.

The Brazilian driver lost control of the rear of his car under braking for turn one with television replays showing the rear wheels sliding just before the drag reduction system wing flap shut at the end of the start/finish straight.

With Massa a passenger he slid into the crash barriers and suffered heavy damage to the rear of his car with both rear wheels, rear wing and exhaust system being ripped off.

"The accident was nothing to do with me, it was a problem with the rear wing, the DRS," Massa said. "When I braked I even switched it off myself before the braking zone, but it didn't close so when I braked the DRS was almost 100% open and I had no grip on the rear so that is why I crashed."

Williams is running a new rear wing for the Canadian Grand Prix this weekend and is analysing the failure. Massa missed the remainder of the first practice session but was able to enjoy a full FP2 in which he finished 13th fastest.

"It's a shame because crashing like that at the beginning of the day is definitely a pain for everybody, for the team, for me as well," he said. "The afternoon was OK, for sure I didn't have everything we can have in the car for the performance in the afternoon because of the crash.

"I am really looking forward that tomorrow everything will be in the car and we can be competitive. The car showed reasonably good pace straight away so I think that's positive and I hope it can be even more positive for tomorrow."