BEIJING -- Brake failure and a flat tyre have been blamed for Taiwan's worst bus accident in 20 years which claimed 22 lives at the weekend.

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A tour bus tumbled into a steep ravine in a mountainous area in southern Taiwan on Sunday, killing 22 and seriously injuring 21 others, according to news reaching here from Taipei.

The accident took place when the bus wound its way down the mountain road at Meiling in Tainan County.

After inspecting the wreckage on Monday, Tainan prosecutors said that the bus could have lost control because of brake failure and a flat rear right tyre based on the tracks left by the bus.

Some investigators said that the driver might have driven too fast downhill and others said that the old bus, with its recycled tyres in use, should also be blamed for the tragedy.

Prosecutors found that the tread design of the four tyres was worn out and they were all recycled ones.

Taiwan's transport agency said they would amend relevant regulations to ban the use of recycled tyres on buses and tour buses older than 14 years.