A man arrested in connection with the murders of two French students who were tortured and then set on fire has been taken to hospital suffering from burns to his arms and hands.

The 33-year-old gave himself up to police this morning, but detectives had to wait to interview him while he was assessed and treated by doctors for most of the day and evening.

His arrest was described as a "significant development" by police sources. Officers have not ruled out the possibility that more than one person may have been involved in the murders of Laurent Bonomo and Gabriel Ferez, talented 23-year-old biochemistry students, who were found nine days ago at a flat in southeast London.

They had been tied up and stabbed nearly 250 times before their bodies were set on fire. Five hundred students from across France today returned to the Polytech Clermont-Ferrand, a week after the start of their holidays, for a march in memory of the murdered pair.

Many said that they were reconsidering plans to continue their studies in London after the murders of Mr Bonomo and Mr Perez. Mr Bonomo had been president of the Federation of the city's 15,000 students until February. Walking behind a banner reading "From all the corners of the world the second-year biological students think of you and those close to you", groups of tearful friends comforted each other as they walked the two miles to the city centre. Mr Bonomo's father, Guy, today spoke for the first time to support the police investigation. "I have every confidence in Scotland Yard," he said, adding that he was too distressed to comment further at present. The 44-year-old commercial director, his wife, Lydie, 52, and their young daughter Ambre are being comforted by friends in Paris.

Mr Bonomo, who was studying the proteins that cause infectious disease, had been stabbed 196 times, with up to half the wounds inflicted after he had died.

Mr Ferez, who hoped to become an expert in eco-friendly fuels, had 47 separate injuries. They had come to London to develop their skills as specialists in infectious disease and environmental engineering.

Detectives are trying to put together what the two students did in the hours before they were found in Mr Bonomo's bedsit.

Officers are following up dozens of new leads after an appeal for information at the scene on Sunday night. They are also exploring the possibility that the pair were killed by the same burglar who targeted the premises six days before the murders.

In the first burglary Mr Bonomo's laptop was stolen. During the second attack two Sony PSP games consoles were taken. Another line of inquiry is the possibility that the pair had been tortured for the PINs of their bankcards.

Experts have found no evidence of forced entry, suggesting that keys might also have been stolen during the first raid.