The badly burned bodies of Laurent Bonomo and Gabriel Ferez, both 23, were found with more than 240 stab wounds.

Police said the men's bank cards may have been taken along with two Sony PSP games consoles.

A laptop had been stolen from the flat in Sterling Gardens, New Cross, south London six days earlier.

Officers received 25 calls in response to their appeal for information and police have been "following these up".

Det Ch Insp Mick Duthie said: "We are keen to hear from anyone who has recently been offered the a laptop and two personal game consoles, or knows someone who has unexpectedly come to have them.

"A black Packard Bell laptop was taken during a burglary that took place between 0500 and 0600 on the morning of 23 June, 2008. Someone entered the living room of 12 Sterling Gardens and stole the computer.

"Laurent Bonomo said he was in the shower when he heard a suspicious noise. He found the window of his living room forced open and his laptop was stolen.

"The search of the address is not yet completed, but we have established that two Sony PSPs are missing and believe they were taken during the incident on Sunday when the two men were killed," he said.

The French news agency AFP reported one woman as having seen two men banging on the window of the flat on Sunday, the day the students' bodies were found.

Mr Duthie said the men's injuries were horrific, adding it was possible they had been tortured.

Police also said the attacker, who may have been using hard drugs, had started a fire after the killing and an explosion was heard from the property.

A man described as white was seen running from the bedsit rented by Mr Bonomo.

There were no signs of forced entry and it is possible another set of keys was used to gain entry to the flat.

On Thursday Mr Duthie said: "Everyone working on this case, including myself, has been deeply shocked by what we have seen.

"I have never seen injuries like this throughout my career."

Another line of inquiry is that their deaths could have been the result of mistaken identity as police "cannot find anything in these two young men's background to suggest they were involved in any criminality".

Mary Bertez, Mr Bonomo's fiancee, last saw Mr Bonomo on Sunday morning.

Writing on a social networking site, she said she would help police with the inquiry so he could "be avenged".

She wrote they had "10 months of a happiness I had never experienced until then" and she would "never stop thinking about" him.

The biochemistry students had been involved in a research project at Imperial College, London, and were due to return home to France later this month.

Imperial's Rector Sir Roy Anderson said the university had been left in shock by the deaths of the students who had "bright futures ahead of them and it is dreadful that their lives should end so soon".

BBC