The IOC's medical chief insists he has no reason to have suspicions over the latest Chinese swimming sensation Ye Shiwen.

China's appalling past record for their swimmers failing doping tests has led to inevitable suspicions over the 16-year-old, who took five seconds off her personal best and more than a second off the world record in the 400m individual medley.

The swim was described as "insanely fast" by previous world record holder Stephanie Rice - indeed in the final 50m Ye swam faster than the men's champion Ryan Lochte.

But IOC medical commission chairman Arne Ljungqvist, a veteran anti-doping competitor, did not express any concerns when asked if he had any suspicions regarding the swimmers in London.

Ljungqvist said: "I am pretty experienced in this matter, as you know, and have been at the Games since a long time and within anti doping for 40 years.

"You ask me specifically about this particular swimming. I say no, I have not personally any reason other than to applaud what has happened, until I have further facts, if so.

"Should I have my suspicions I keep them for myself, first of all, and take any action, if so, in order to find out whether something is wrong or not."

The amazing improvement in performance will have alerted doping control officials however for target-testing.

London 2012's head of anti-doping Jonathan Harris confirmed: "Enhancements in performance is something we focus on so we target those athletes."

If China are unhappy about their new champion being the focus of any suspicion, they only have their own record to blame. During the 1990s they had 40 swimmers test positive for banned substances, and seven before the Beijing Games in 2008.

As recently as last month, 16-year-old world champion in the 4x100m medley Li Zhesi tested positive for the blood boosting drug EPO.

Rice, from Australia, would not be drawn on whether she thought Ye was legitimate.

She said: "I have no idea, I mean I wouldn't want to get into that at all, but a 58 is an insanely fast swim, but I know she's a good freestyle swimmer.

"I swam next to her at worlds in the 200 IM last year and she came home over the top of me in that freestyle leg and I'm not exactly a bad freestyler, so she's a gun in freestyle."

Ye was back at the Aquatics Centre this morning for her heat. She was easily quickest in the 200m individual medley, in which she is world champion, her time of two minutes 08.90 seconds, 1.61secs ahead of Kirsty Coventry.

Meanwhile, Harris revealed that cleaners and security staff in the Olympic Village had been briefed to report any evidence of doping by athletes, such as needles or discarded medication packets.

"If they should come across any practices of paraphernalia they would bring it to our attention," he said.

He added that the anti-doping effort was now heavily reliant on the use of intelligence with any new information discussed on a daily basis with UK Anti-Doping.