Narain Karthikeyan's heavy crash in the Belgian Grand Prix was caused by a wheelnut problem at his second pitstop.
The Indian went off at Stavelot on his 30th lap, spinning into the barrier and ending his race.
"Something went wrong with the pitstop," Karthikeyan told AUTOSPORT. "The bolt was cross-threaded and then it came off.
"I was lucky it didn't come off at Eau Rouge or something like that.
"I didn't feel it at first, but a few tenths before the accident I felt the front going and it happened too quickly for it to be possible to react. By then, it was already making me spin."
The Indian suffered a knock to his left foot in the impact but this will not cause him any problems at Monza.
"It was a big impact and there was a knock to my foot, but it will be fine for Monza," he said.
"What happened is a shame because up to that point we were having a good race."