By Ian Ransom

LONDON (Reuters) - The IOC demanded a probe into the coaches of eight disqualified players, dashing world badminton's hopes of drawing a line under a match-throwing scandal that has damaged the sport's credibility at the London Games.

The Badminton World Federation (BWF) also said it would review video of all round-robin matches at the Olympic tournament, after competing teams slammed the format as ripe for manipulation.

The investigations overshadowed spirited competition on Day Six at Wembley Arena, with players contesting furiously to qualify for the medal rounds.

The International Olympic Committee asked China, South Korea and Indonesia's national delegations to probe the entourages of the four women's doubles pairs who, in farcical scenes on Tuesday, tried to lose their matches to secure an easier run through the knockout rounds.

"Now we make sure they (the three national Olympic committees) also consider the entourage, to make sure it is not just the athletes who are punished for this," IOC spokesman Mark Adams said. "They are looking into this."

The announcement followed an admission by China's head coach Li Yongbo that he was culpable for his top-seeded pair of Yu Yang and Wang Xiaoli deliberately playing to lose in the women's doubles.

The IOC's move and Li's comments to state TV undermined the BWF's claim that the coaches had no case to answer.

BWF chief Thomas Lund said the sport needed an "education process" but declined to say whether the federation would follow up on Li's admission.

The IOC said the eight women players were being removed from the athletes' village and having their accreditations revoked.

PUBLIC APOLOGY

Yu announced she was quitting the sport in a post on her Chinese microblog, slamming tournament officials for shattering her and her partners' Olympic "dream".

After being ordered by her delegation to publicly apologize, she appeared more contrite in an appearance on Chinese state television along with head coach Li.

"First of all I want to apologize to our fans. We didn't play with the Olympic spirit... So it has reflected very badly on us," she said.

China's remaining players slated their team mates' expulsion. "I think it's extremely unfair. Firstly, it's a problem with the format, that's what I believe," fumed Xu Chen, who will partner Ma Jin in the mixed doubles.

Despite losing Yu and Wang, China's bid for an unprecedented sweep of the five Olympic titles remained intact even though the near-packed crowd invariably sided with their opponents.

Canada's women's doubles pair Alex Bruce and Michele Li were on the verge of a fairytale appearance in the final after being reinstated to the competition following the disqualifications.

DENMARK GLOOM

But fourth-seeded Japanese pair Mizuki Fujii and Reika Kakiiwa rallied to close out their match 21-12 19-21 21-13 to deflate the rowdy Canadian supporters.

Indian fans celebrated when fourth seed Saina Nehwal, her country's greatest hope of a maiden badminton medal, edged Dane Tine Baun to set up a semi-final against Chinese world number one Wang Yihan.

Nehwal stood defiant among three China players in the last four. "I feel like I'm Chinese!" she laughed.

It was a gloomy day for Denmark, however. Fifth seed Baun blew three game points to slump out after being distressed by a line call.

Her fiery team mate Joachim Fischer smashed his racket to smithereens off court after losing in the mixed doubles.

"Why did I do that? Because I lost!" he snapped, after dunking the pieces in a bin.

Indonesia's proud record of a badminton gold medal at every Games since the sport's introduction in 1992 came to an end when third seeds Liliyana Natsir and Tontowi Ahmad lost in the other mixed doubles semi-final.

Danish veteran Peter Gade bowed out of his last Olympics aged 35 with a battling quarter-final loss to China's Chen Long, while men's singles champion Lin Dan survived a scare against Japan's plucky sixth seed Sho Sasaki.

Lin will meet South Korean Lee Hyun-il for a place in the final. Malaysia's top seed Lee Chong Wei, who has been dogged by an ankle injury, trounced India's Kashyap Parupalli for a berth in the other semi-final.

(Editing by Ken Ferris)