The Rapid KL bus driver who rammed into several vehicles along Jalan Ampang last night was under the influence of drugs, said police.

Kuala Lumpur police chief Mazlan Lazim said this is based on the preliminary investigations into the case whereby drug tests conducted on the 32-year-old driver showed that he tested positive for methamphetamine.

However, Mazlan said police are still looking into whether the suspect has a history of substance abuse.

The bus driver was believed to be in a panic last night when the bus he was driving grazed a roadside burger stall and the stall operator and a group of motorcyclists gave chase.

The bus driver sped off and crashed into seven cars along Jalan Ampang before the vehicle came to a halt at the Jalan Ampang-MRR2 junction.

Based on the video footage of the incident which went viral on the social media, the bus driver was severely assaulted and he was taken to the Ampang hospital.

It is learned that he has been discharged from the hospital at about 1.30pm today, but at the time of writing, KL traffic police chief Assistant Commissioner Zulkefly Yahya had informed the media that the suspect was having his statement recorded at the traffic police station.

When asked whether the police would take action against those who assaulted him, Mazlan said it depends on whether the bus driver lodges a police report against them.

"If he (the bus driver) lodges a report, we will investigate," he said, when met at the opening of Crime Prevention Patrol Unit at Esplanade KLCC today.