Police say the No. 2 Zimbabwean opposition official will be charged with treason, which can carry the death penalty.
Police say documents linked to Tendai Biti, secretary-general of the Movement for Democratic Change, discuss changing Zimbabwe's government. Party officials say separately that MDC leader Morgan Tsvangirai has been detained again at a roadblock and taken to a police station.
Biti was arrested Thursday at the Harare airport upon returning from South Africa.

Police spokesman Wayne Bvudzijena says Biti will also be charged with making false statements, a charge that refers to accusations he announced election results before the official count was released.
THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.
HARARE, Zimbabwe (AP) - Party officials say opposition leader Morgan Tsvangirai has been detained again in Zimbabwe.
Officials for the Movement for Democratic Change say police detained Tsvangirai at a roadblock in southern Zimbabwe. They say he's been taken to a police station.
It's the third time Tsvangirai has been detained by police since returning to Zimbabwe to campaign before the June 27 presidential runoff.
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