A ROTI prata supper for four polytechnic buddies ended with two of them killed in a horrific car accident on Tuesday night.

They were on their way in a Mitsubishi Lancer to meet another friend after the supper when the car, driven by a Republic Polytechnic student, went out of control along Old Upper Thomson Road, plunged downhill and slammed into a tree.

The two backseat passengers - Mr David Li, 18, and Mr Mervin Teo, 19, both second-year engineering informatics students of Nanyang Polytechnic, died while the driver and front seat passenger, who is also from Nayang Poly, survived with injuries.

Rescuers from the Singapore Civil Defence Force took more than 30 minutes to extricate the trapped two rear passengers.

Mr Li died on arrival at the Singapore General Hospital, and Mr Teo shortly after.

The 19-year-old driver escaped with slight injuries, probably saved by the airbag.

He was discharged from SGH on Wednesday morning. His front seat passenger, Mr Tan Han Leng, 20, suffered cuts and hand injuries and is undergoing surgery at the hospital.

Mr Li was cremated on Wednesday afternoon at Mandai crematorium.

The accident happened at 11.45 pm as the car, a Mitsubishi Lancer, was travelling along Old Upper Thomson Road towards the Seletar Expressway.

It is believed that the two dead students were not wearing seat belts.

Madam Linda Loh, 58, mother of Mr Tan, told The Straits Times on Wednesday that her son suffered injuries on his left hand and had to be operated on.

She said all the four were "as close as brothers" and they were going to meet another Nanyang Polytechnic student who had just passed his driving test after their supper when the tragedy struck.

Speaking to The Straits Times at SGH, Madam Loh, an administrator, said her son called her from the accident scene around midnight.

"He sounded panicky and just told me 'Mom. Accident. I am okay but my two friends are critically injured. He just hanged up," she recalled.

The student who was waiting for the four friends was also told about the accident and he immediately went to pick up Madam Loh from her condominium at Serangoon North Avenue. They rushed to SGH and found out that Mr Li and Mr Teo had died.

Anyone with information on the accident can call the Traffic Police at 1800-547-1818.