The first mission of the commission will debate whether there is a case against Rousseff, following an impeachment vote against her in the Chamber of Deputies on April 18, Xinhua news agency quoted Raimundo Lira, chairman of the commission from the Brazilian Democratic Movement Party (PMDB), as saying on Monday.
If the commission votes in favour and a senate plenary hearing ratifies this decision in a vote set for May 12, Rousseff will have to be removed from office for 180 days while Vice President Michel Temer becomes interim president.
PMDB Senator Antonio Anastasia was elected as rapporteur, despite protests from Workers' Party senators, who only have five seats on the commission.
The commission now has 10 days to elaborate and present its report on whether the impeachment process should go ahead or not.
Rousseff, against whom no formal charges have been presented, is reportedly being investigated for signing budget documents without the right funds to back them up and for delaying payments to state banks, allegedly to cover up the true state of her government's finances.(IANS)