PORT-AU-PRINCE -- Haiti's Senate voted just after midnight Friday to dismiss Prime Minister Michele Pierre-Louis, following almost 10 hours of debate.

Senate President Kely Bastien, who is not allowed to cast a vote under Senate rules, said a letter will be sent to President René Préval notifying him of the Senate's 18-0 decision.

A number of senators who opposed the move to fire Pierre-Louis had left the Senate floor shortly before the vote, believing that they had successfully filibustered the attempt when the clock struck midnight here.

``There is nothing illegal about the vote,'' said Bastien, adding that Haiti ``could have a new prime minister as early as today or Saturday.''

The session began almost two hours after the scheduled start time and lawmakers spent hours debating procedures with supporters of Pierre-Louis, who questioned the validity of the senators' move to censure her.

Her supporters made impassioned pleas and cries of ``illegal'' and ``unconstitutional'' from the Senate floor.

Senators have accused Pierre-Louis, a favorite of the international community, of not moving quickly to solve Haiti's crucial problems: high unemployment, lack of significant foreign investments and environmental deterioration.

Pierre-Louis, in office for a year, said she has spent much of her tenure getting international support for Haiti after four back-to-back storms devastated the country last year, and it is too soon to see the results of her work.

Senators were not swayed.

But unlike the last censure of a Haitian prime minister -- Jacques-Edouard Alexis in April 2008 following days of food riots -- this one wasn't as swift or orderly.

At times, chaos reigned: Lawmakers screamed and talked over one another in front a national television audience.

The Senate president often rang a small silver bell in a futile attempt to create order as the session stretched into Friday morning without a vote. The vote finally occured at about 12:15 a.m., long after Pierre-Louis' Senate supporters had left, believing they had succeeded in preventing a vote.

``There is an error in the summons and everyone knows it,'' said Sen. Youri Latortue, a Pierre-Louis supporter who last year successfully led the movement to oust Alexis.

But those lined up against Pierre-Louis weren't moved by the constitutional arguments, nor her letter to the Senate president questioning the validity of the censure and informing him that she did not plan to attend the session.

``Do we not have the right, the freedom today to call the government and ask for an explanation?'' asked Jean Hector Anacasis, one of the senators leading the effort to oust Pierre-Louis.

Sen. Joseph Lambert, the former president of the senate and leader of President Préval's Lespwa Coalition, went even further, accusing Pierre-Louis of not improving the lives of most of the country's estimated nine million citizens who live on less than $2 a day.

``I've never been so shocked in my life,'' said Sen. Andris Riche after hearing Lambert's reasons for wanting Pierre-Louis gone and walking out of the session following an impassioned speech in support of her.

``You are going to commit an act that to me is disastrous. Decisions are not made at the prime minister's office. You know where the decisions are made,'' he said, implying the presidential palace.

Neither Pierre-Louis nor her government showed up for the censure.

Miami Herald special correspondent Jean-Cyril Pressoir contributed to this report.