Tokyo - Rugby officials announced a change to concussion procedures at the World Cup on Sunday, a day after New Zealand's Sam Cane was told he had spent too long having a head injury assessment and couldn't return to play.

World Rugby said the 10-minute window allowed for an HIA would now start when players reach the assessment room, rather than as they leave the pitch.

All Blacks flanker Cane went off in the first half against South Africa but had to cross the 72,000-capacity International Stadium Yokohama for his HIA, meaning he couldn't get back in time despite passing the test.

"Specifically for Rugby World Cup, with immediate effect, the official 10-minute HIA window will commence from the moment the temporarily replaced player enters the HIA room, rather than when the player leaves the playing area," a World Rugby statement said.

"This is to facilitate slightly longer distances to the HIA room from the field of play at some of the venues."

New Zealand coach Steve Hansen admitted he wasn't "overly happy" about the Cane incident and that he had asked for clarification about the rules.

"Last night Sam... had to cross over to the other side of the stadium for an HIA," said Hansen, after the 23-13 Pool B win over the Springboks.

"But we've had notification that the clock doesn't start until you get to the actual room itself. I wasn't overly happy last night to have one of our best players missing 40 minutes of the game, but I'm just glad they sorted it out."