The comedian and former Tonight Show host told a Las Vegas Review-Journal columnist on Thursday that he broke his collarbone and two ribs and cracked his kneecaps on January 17.

The November garage fire and January wreck both stemmed from his passion for working on vintage vehicles.

He suffered burns on his face, hands and chest in a petrol fire while repairing the fuel line on a vintage car.

Last week, it was a vintage motorcycle.

He told the Review-Journal's John Katsilometes he was testing a 1940 motorcycle when he noticed the scent of leaking petrol.

"So I turned down a side street and cut through a parking lot, and unbeknownst to me, some guy had a wire strung across the parking lot but with no flag hanging from it," Leno, 72, said.

"So, you know, I didn't see it until it was too late."

He insisted he was OK and would even be working this weekend, adding that the intense coverage of the November fire made him reluctant to say anything in the days since last week's accident.

Leno took over NBC's Tonight when longtime host Johnny Carson retired in 1992.

He was succeeded by Conan O'Brien in 2009 but NBC got cold feet when the show's ratings dropped and brought Leno back as host in 2010.

He remained in the job until Jimmy Fallon took over in 2014.

Leno turned his love of cars into a CNBC series, Jay Leno's Garage, and hosts a revival of the game show You Bet Your Life.

He was hospitalised for nine days after the fire but was back performing stand-up at a Southern California club six days after his release, People reported last year.

Australian Associated Press