Police officers inspect a car that crashed into pedestrians and other vehicles in Seoul City Hall, July 2. Yonhap

Suspicions are deepening over the cause of Monday's deadly car crash that claimed nine lives and injured four others, as some experts do not rule out the possibility of careless driving by the perpetrator who claimed sudden unintended acceleration as the cause.

Surveillance camera footage shows a Hyundai Genesis sedan driven by the 68-year-old man went against traffic about 200 meters after leaving a hotel near Seoul City Hall at 9:27 p.m. Monday before striking two vehicles and many pedestrians, crossing an intersection and stopping near City Hall Station.

The man, a bus driver by profession, claimed his vehicle suddenly accelerated unintentionally, saying in a media interview that he kept applying the brakes, but the car did not respond.

But some experts are raising suspicions over his remarks, as the sedan appears to have slowed down and stopped by itself. Usually, they note, vehicles undergoing sudden unintended acceleration go out of control and end up colliding with a wall or street lamp.

"Considering many circumstances, the possibility of the driver's carelessness or inattention, rather than sudden unintended acceleration, should be looked into," said Yeom Gun-woong, a professor at U1 University. "It is difficult to assume that a car abruptly shifts from unintended acceleration to normal operation after an accident and stops," Yeom said.

He said sudden acceleration usually involves evasive movements to avoid hitting vehicles or people, but those were not seen at all in Monday's accident. "It's possible that the driver may have panicked after entering the one-way road in reverse and hit the accelerator, trying to get off the road quickly.

Kim Pil-soo, an automotive technology professor at Daelim University College, said it is difficult to determine whether the cause of the accident was sudden unintended acceleration or not.

"It is difficult to determine the cause of sudden acceleration accidents, and sometimes people make excuses because they are reluctant to admit their own mistakes. At age 68, a man cannot be considered a super-elderly person, meaning there's a small possibility of weakened abilities to operate devices or make decisions," Kim said.

But Park Byung-il, a renowned automotive technology master, said the possibility of sudden unintended acceleration is quite high, considering the scale and condition of the accident and the severity of the crash.

If the revolutions per minute rapidly increases due to sudden acceleration, Park said, the vehicle tends not to respond even if the electronic brakes are applied. (Yonhap)