(Reuters) - A 100-year-old motorist lost control of his automobile as he backed out of his driveway into a crowd of children and parents outside an elementary school in Los Angeles on Wednesday, injuring nine children and two adults, authorities said.

Four of the children initially were listed in critical condition, though most were upgraded after they arrived at the hospital, and none appeared to have suffered life-threatening injuries, authorities said.

The pedestrians were standing around a sidewalk vendor's cart when the car rolled up over the curb in front of Main Street Elementary School in south Los Angeles as classes were letting out at about 2:30 p.m. local time, police said.

The driver, who was detained for questioning and later released without being charged, told police his car experienced some kind of mechanical failure, Los Angeles Police Department spokeswoman Karen Rayner said.

"At this point, it doesn't appear as though there are going to be any charges filed, but it's an ongoing investigation," she said. "We'll definitely be looking at his competency to retain his driver's license."

His car also was impounded as evidence, she said.

Authorities did not release the motorist's name. But the driver gave his name to local television station ABC7 as Preston Carter and said he turns 101 next month. He also told the TV station that his brakes failed as he was backing up.

At least one of the nine children injured in the accident remained in critical but stable condition Wednesday night at County-University of Southern California Medical Center in Los Angeles, a hospital spokeswoman said.

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