Rescuers attempt to free people trapped in the rubble
A school has collapsed in a suburb of the Haitian capital Port-au-Prince, killing at least 50 people and trapping an unknown number under the rubble.
Hundreds of rescuers are working to free people from the wreckage of the school. Between 200 and 700 children are thought to have been inside.
More than 120 people have also been injured in the collapse.
Haiti's president has visited the three-storey building, where relatives of missing pupils have been gathering.
The church-run school, La Promesse College, is located in the suburb of Petionville.
The site contains a kindergarten as well as a primary and secondary school.
While there was no official comment on the possible cause of the collapse, reports say that the upper floor of the school was still under construction.
Many people are feared to be under the debris
The BBC's Andy Gallacher says residents in the area suspect that the school was poorly rebuilt after it partially collapsed several years ago.
Associated Press quoted police as saying that the preacher who ran the school could face criminal charges.
President Rene Preval met relatives, while officials said an investigation would be launched.
"We are going to ask the minister of education to make an inspection of all the schools built in the same way," Senator Yvon Bissereth told AFP.
As rescuers clawed at the rubble with tools or their bare hands, Matt Marek, head of programmes for the American Red Cross in Haiti, said he thought the death toll would go much higher.
"This is going to be an all-day affair," he said.
United Nations peacekeepers and members of the Haitian Red Cross were at the scene, trying to create an access route through the crowds so that UN military engineers could approach.
The neighbouring Dominican Republic promised to send two helicopters to help the rescue effort.
"It's like an earthquake," said Brazilian Maj Gen Carlos dos Santos Cruz, commander for UN troops in Haiti.
"You have a lot of people under the debris. We don't know how many exactly but there are a lot of people there because they were attending school."
A Haitian Red Cross worker, Michaele Gedeon, described a scene of horror for CNN television: "The whole school collapsed on the kids, and you know on the phone you can hear so many, so many children, you know, crying, crying. And saying, 'This one is dead, that one is dead'."
A mother who rushed to the school in fear of her child's safety said the disaster had struck at 1000 local time (1500 GMT).
The building's first floor collapsed and "dragged down the rest of the building as the pupils were in class", she told AFP news agency.
Wendell Theodore, a correspondent for Haiti's Radio Metropole, said that the second floor of the school was still under construction when it fell in.
"There are two floors that were packed with children," he told French radio station France Inter.
"The third [second, in English terms] floor was still under construction, construction that wasn't complete of course. Several people agree that this could be behind today's accident."
The Mayor of Petionville, Claire Rudie Parent, said she suspected a "structural defect" had caused the second floor to collapse on to the first.
She told AP she doubted the recent wet weather had contributed to the collapse.
Correspondents say Haiti is the poorest nation in the western hemisphere where mudslides and poor construction are commonplace.
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