Police are asking for witnesses after two French bio-engineering students were stabbed multiple times, tortured and burned in their London apartment, the Times of London reported Thursday.

One of them, Laurent Bonomo, was stabbed 196 times, the detective leading the murder investigation said. His friend Gabriel Ferez suffered nearly 50 stab wounds, authorities said while speaking on condition of anonymity in line with police policy. Investigators believe an accelerant was used, possibly in an attempt to destroy evidence, Britain's Press Association reported.

Neither student had a criminal record.

"I have never seen injuries inflicted to bodies like this before," Detective Chief Inspector Mick Duthie told reporters at a news conference.

Authorities appealed for witnesses in the attack, which took place late Sunday. Authorities found the bodies after responding to reports of an explosion and fire, but only learned how the students died after the post-mortem examination results were delivered Wednesday.

"We are here today because I don't know why these boys were killed or who killed them," Duthie said. "I do believe, however, that those responsible must have been bloodstained when they left."

London has been gripped in recent weeks by a series of stabbing cases involving young people, leading to much soul searching about what has gone wrong with city's troubled youth. But the case of the French students is unique because the pair are foreigners and because of the brutality of the crime.

For a major capital, London has a low murder rate. Police say there were 159 homicides from April 2007 to the same month this year, about a third the number of New York, which is similar in size.

Authorities declined to speculate what might be behind the crime before further toxicology and other tests were completed.

The students were both 23 and in the second year of a three-year Master's degree in bio-engineering in France and had been selected to take part in a three-month research project into DNA at London's Imperial College. They were within weeks of returning home.

"Laurent and Gabriel had bright futures ahead of them, and it is dreadful that their lives should end so soon," Imperial College Rector Sir Roy Anderson said. "I would also like to offer my support to the Imperial community as we mourn the loss of two young members."

Click here for more on this story from the Times of London.