PORT-AU-PRINCE: Prime Minister Michele Pierre-Louis was removed from office by the Haitian Senate shortly after midnight Friday, in a move that could imperil efforts to attract foreign investment to the storm-wracked, impoverished country.

The vote of 18 of 29 senators to censure Pierre-Louis most voting against her were members of President Rene Preval's party also dissolves the cabinet. Political instability could imperil efforts by the international community and Haitian leaders, including Pierre-Louis, to attract foreign money to the embattled Caribbean nation.

Most of those voting against the prime minister, who is Haiti's head of government and was nominated by Preval last year, were members of Preval's own Lespwa party. They took control of the Senate just weeks ago after winning June elections praised by some international observers but marred by low turnout and fraud allegations.

Debate raged for more than nine hours, with senators storming out of the room, accusing each other of carrying weapons and marching up and down the aisle of the narrow chamber as Senate President Kelly Bastien rang a silver bell to call for order.

But almost no time was devoted to discussion of the prime minister herself. Instead supporters — including some like opposition Sen. Youri Latortue who held up her nomination last year — spent hours denouncing the process as illegal because of alleged procedural errors.

Those planning to vote against her rarely spoke, and when they did usually just asked Bastien to call for the vote.

Pierre-Louis took office in September 2008 as Haiti was being pummeled by one of four tropical storms and hurricanes that killed nearly 800 people, left tens of thousands homeless and caused $1 billion in damage. She filled a post that had been vacant for five months after senators dismissed her predecessor during riots over the high cost of food.

She refused to attend the Thursday session, saying in a letter that the result was a foregone conclusion. Several senators denounced her for not attending, and a special vote had to be taken to allow the censure to take place in her absence.

"It is an insult that she decided not to come," Sen. John Joel Joseph, a member of President Rene Preval's Lespwa movement, told reporters.

Pierre-Louis explained her decision in a letter to Senate President Kelly Bastien.

"At a time when efforts are under way for Haiti to join the international community and it has possibilities of investment, national and international, to better the lives of the Haitian population ... my government decides not to participate in this hearing," she wrote.

She added, "I leave the senators of the republic to face their responsibility in front of the nation."

The hearing surprised many when it was announced last week.

As is often the case in politically tumultuous Haiti which in the past five years has ousted a president in a bloody rebellion and gone through four previous prime ministers the exact nature of the challenge against Pierre-Louis is not clear.

Questioning was expected to focus on the use of $197 million government storm-recovery fund consisting of savings from the Venezuelan-sponsored Petrocaribe program, which provides oil and gas at preferential prices.

It is not clear how the funds were spent, or what those who voted against Pierre-Louis believe she did wrong. It is unclear if the president, who distanced himself from those politicians during their campaigns, is backing the challenge.

But opposition senators, who in a reversal find themselves supporting the embattled government, point to the chief executive as the one who requested the hearing.

"Senators of the president's party tell us that," Sen. Youri Latortue said. Latortue held up Pierre-Louis' nomination last year but said he would support her Thursday.

The U.S. Embassy in Port-au-Prince said U.S. Secretary of State Hillary Clinton phoned Preval last Friday, after senators issued their summons to Pierre-Louis. Spokeswoman Mari Tolliver declined to give details of the conversation, but struck a cautionary tone Thursday.

"We have made it known to the Haitian government that the perception of instability could be very damaging to Haiti at this time," Tolliver said.

Pierre-Louis, an educator who headed the Haitian branch of George Soros' Open Society Institute, is well-liked by diplomats but has no real political base.

Preval is expected to select another prime minister quickly to continue momentum on projects aimed at building garment factories and roads and boosting agriculture. But he is no stranger to governing alone: during a previous term in the 1990's he left the post vacant for 18 months after his prime minister resigned.