AFP - Haitian police detained 10 members of a US Christian charity group after they allegedly tried to leave the country with more than 30 children who survived the country's devastating earthquake.

News of the arrests came as the UN's food agency prepared to launch a massive food effort targeted at vulnerable women in a bid to ease some of the chaos surrounding the relief effort for the January 12 disaster.

Police seized five men and five women with US passports, as well as two Haitians, as they tried to cross into the neighboring Dominican Republic with 33 children, aged between two months to 14 years, late Friday, Haitian authorities said.

Border police "saw a bus with a lot of children. Thirty-three children. When asked about the children's documents, they had no documents," Haitian Culture and Communications Minister Marie Laurence Jocelyn Lassegue said.

Speaking in her detention cell near Port-au-Prince airport, Laura Silsby, head of the Idaho-based New Life Children's Refuge charity, said the group's aims were entirely altruistic.

"We came here literally to just help the children. Our intentions were good," Silsby told AFP. "We wanted to help those who lost parents in the quake or were abandoned."

But the director of the Haitian center where the children are being cared for said earlier Sunday that most of the youngsters insist they still have family.

Some of the older children had spoken to aid workers and "say their parents are alive, and some of them gave us an address and phone numbers," said Patricia Vargas.

The US embassy in Port-au-Prince said the group were being held for "alleged violations of Haitian laws related to immigration."

Haitian officials have warned that child traffickers could take advantage of the chaos after the quake, and that legitimate adoption agencies may rush to take orphans before proper checks have been conducted.

"Everything is disorganized since January 12 and some people are using it to devote themselves to a veritable trade in children," said Jeanne-Bernard Pierre, director of Haiti's Institute of Social Welfare.

Workers from aid groups and other non-governmental and religious organizations have poured into Haiti in the aftermath of the quake which is believed to have killed some 170,000 people. Related article: Big business urged to help

Amid fears that food is not reaching enough people, the World Food Program said it would open 16 fixed collection sites in Port-au-Prince on Sunday, aiming to feed two million people in two weeks.

Only female quake survivors will be allowed at the sites to avoid scenes at chaotic mobile handouts that have sometimes seen children and women muscled aside in the scramble for bags of rice, beans and cooking oil.

The aid effort suffered a further setback over the weekend, after the US military stopped flying injured Haitians to the United States for treatment because of a dispute over costs.

The governor of Florida has asked the US government to share the financial burden on his state's hospitals, putting a block on flights that have so far carried more than 500 people with spinal injuries, burns and other wounds.

The United States has spearheaded relief efforts since the 7.0-magnitude quake, which also injured around 200,000 and left more than one million homeless.

The aid effort has, however, drawn criticism for a lack of coordination. Related article: Historic Haiti market burns

Haitians, many of whom are living in squalid makeshift tent camps, have complained that relief has been slow to reach them on the ground.

Haitian Prime Minister Jean-Max Bellerive made a fresh appeal for 200,000 tents before the country's rainy season starts, most likely in May.

"We are very aware of the consequences to all of the people on the streets if it's starting to rain," Bellerive told CNN, adding that the government only had 3,500 tents so far.

Diseases such as diarrhea, measles, and tetanus are rising in tent camps, prompting UN agencies and the government to prepare a mass vaccination drive, while survivors also face rising insecurity with reports of rape and violence.

Aid officials have warned meanwhile that the reconstruction process in Haiti, already the poorest country in the Americas before the quake, will take decades.