UPDATE 6-Brazil corruption probe widens; Senate leader, BTG Pactual CEO arrested
* Top court orders arrests for obstructing probe
* Shares drop as much as 39 pct; bonds tumble
* Amaral is ruling party's leader in the Senate
* Clients withdraw funds from BTG (Updates share fall, adds BTG clients withdraw funds, Senate action, comment by senator's lawyer in paragraphs 3, 8-9, 11-12, 16, 18)
By Guillermo Parra-Bernal and Leonardo Goy
SAO PAULO/BRASILIA, Nov 25 (Reuters) - The chief executive of Brazil's biggest independent investment bank and the leading senator in the governing coalition were arrested on Wednesday on suspicion of obstructing the country's most sweeping corruption investigation ever.
The detention of such prominent power brokers on orders from the Supreme Court raised the stakes dramatically in a bribery scandal that started with state-run oil company Petrobras and now threatens the heights of Brazilian banking and politics.
The arrest of André Esteves, the billionaire CEO and controlling shareholder of BTG Pactual SA and Brazil's most influential dealmaker, sent the bank's listed shares into a dive that wiped out a fifth of its market value and raised red flags at the central bank.
Brazil's Congress also ground to a halt with the arrest of ruling Workers' Party senator Delcidio do Amaral, a veteran lawmaker who has run the economic affairs committee and who has been key to President Dilma Rousseff's unpopular austerity program. Continuación...