Police investigating the savage murder of two French students in London are interviewing a man after he received hospital treatment for burn injuries, Scotland Yard said on Tuesday.

Bio-engineering students Laurent Bonomo and Gabriel Ferez, both 23, were bound, gagged and repeatedly stabbed in Bonomo's south London apartment in what police said were the most "frenzied, brutal and horrific" murders they had seen.

Bonomo was stabbed nearly 200 times, with up to 80 of the wounds inflicted after he was dead, Ferez received nearly 50 knife wounds, with the killer or killers then setting fire to the apartment in an attempt to destroy evidence.

The 33-year-old man, who is the second arrest in the case, handed himself in at a south London police station on Monday, but before police could talk to him he was taken to hospital.

"He was treated for burns and was then discharged and returned to police custody," said a Scotland Yard spokeswoman.

Over the weekend, police arrested a 21-year-old man in connection with the murders, but he was released without charge on Sunday.

"Our appeals for any information in the case remain active," Scotland Yard said.

"We would reiterate that we do not know how many suspects may be involved and no-one is charged with this offence."

A man seen running away from the vicinity of the apartment on the night of the murders has been described by witnesses as white, aged between 30 and 40, slim build and wearing a light coloured baseball cap, dark top, blue jeans and white trainers.

A black Packard Bell laptop computer was stolen from the flat six days before the murders. Bonomo disturbed an intruder who stole the laptop as he took an early morning shower.

Forensic experts have found no evidence of forced entry after Sunday's murders, suggesting that a set of keys might also have been stolen to gain entry on the day of the killings.

Two Sony handheld games consoles were also taken that day. Credit cards are also believed to be missing.

French newspapers said the shocking murders highlighted how dangerous London has become after a spate of teen stabbings this year that has prompted the city's Mayor Boris Johnson to make it a priority and police to expand a specialist knife-crime squad.

Nineteen teenagers have been violently killed on London's streets this year, mostly by stabbing.

London police have arrested more than 1,200 people and seized 528 knives during a six-week crackdown sparked by the growing number of stabbings.