Zamzam camp, Sudan - Every day, a peacekeeper truck pulls into this teeming camp carrying loads of water, and is greeted by long lines of refugees.

It's not the troops' job - but after the expulsion of many aid groups in Darfur, everyone is scrambling to fill the gaps in the safety net that keeps millions of refugees alive.

The expulsion ordered by the Sudanese government could not come at a worse time for Zamzam camp. Even before the order, aid groups were rushing to deal with a massive new influx of refugees from the fighting - 37,000 in the past month, nearly doubling the camp's size.

Now there are fewer clinics to take care of the refugees - at a time of diarrhea outbreak - fewer hands to help build shelters or distribute supplies. There are also fears of violence.

In another northern Darfur Al-Salam camp, armed men looted a storehouse of the one of the expelled agencies, Oxfam, early Saturday.

Khartoum's expulsion of aid workers effectively decapitated the crucial humanitarian network ensuring the survival of Darfurians, amid a 6-year-old conflict that has driven 2.7 million people from their homes and killed 300,000.

The order forced out 13 international aid groups and three Sudanese ones from Darfur and northern Sudan in retaliation for an international tribunal's order for the arrest of Sudanese President Omar al-Bashir on charges of war crimes in Darfur.

The expelled groups made up 40 percent of the aid personnel and included some of the best organized and most experienced agencies dealing with the conflict.

The remaining aid workers say, in the immediate term, they are filling the gaps. But they warn that further on, as early as three months from now, the crisis may start to set in, with deteriorating health and outbreak of diseases - even violence, as desperation grows in the overcrowded camps.

The Sudanese government says the warnings are "premature," insisting it can fill the gap working with U.N. agencies and the remaining groups. But many refugees deeply distrust government aid and suspect that Khartoum just wants to drive them out of the camps.

In Kalma camp, another overcrowded camp in southern Darfur, residents have refused to let in government health workers or alternative foreign aid groups, despite an outbreak of meningitis.

Journalists have also been denied access into the camp, which housed at least six of the expelled aid groups.

In Zamzam camp, where three groups were expelled, government Health Ministry officials are stepping up their role as well as local aid groups, such as the Sudanese Red Crescent.

At the compound of one of the expelled groups, the American CHF International, rolled up straw roofs are piled up in a corner. The group had intended to distribute them to new refugees to help build shelters.

Now, they are being held by the government and refugee women are collecting tree branches and straw to build shelters from the scorching sun.

"Al-Bashir came here and said no more aid groups," said Mohamed Adam, a local guard assigned to watch the unused roofs. "Now the money has stopped ... It is over," he said, describing the government as "stubborn."

Water remains the main concern. A government agency, in cooperation with UNICEF, dug 40 boreholes for wells in the past two weeks, but it's not enough - and more truckloads of refugees arrive every day.

With no one else to do it, U.N.-African peacekeepers, whose mission is security not humanitarian work, have to take up the slack, trucking in 45,000 liters of water a day.

"People are many here. We need more water," said Khadra Ali, 40, who waited for two hours in line for water on Thursday.

With a permanent health clinic now closed, the government has sent in a mobile clinic, but it is struggling to meet demand.

Hawa Hamed, a newly arrived refugee, said she heard of a mobile clinic that came through several days ago, but "today, they didn't come at all."

Hamed, 23, says she was trained as a community health worker by one of the expelled groups, Doctors Without Borders-Holland while she was still in her home region of Muhajeria, in south Darfur. Now, with no supplies or clinic to back her up, she can only offer advice.

Hamed visits 15 families a day, preaching the use of saline water to avoid dehydration. "I go around telling mothers they should clean the containers before they fill them up with water," she said, adding that countless of children have been affected by the diarrhea outbreak and she has already heard of one fatality.

Workers from the remaining aid agencies refused to speak openly about the situation, fearing they too would be expelled. Most U.N. officials were also reluctant to discuss the extent of the needs, saying they were waiting for the results of a joint assessment by the U.N. and the government on the post-expulsion humanitarian situation.

The biggest concern is that recent improvements in nutrition and epidemic prevention will suffer a setback, especially with the rainy season starting in June. Last year was the first one without a cholera outbreak, but deteriorating sanitation could easily see its return.

Ali Youssef, a senior foreign ministry official, decried the international criticism of the expulsion, blaming the March 4 arrest warrant for threatening peace and security in all of Sudan and likened it to "a declaration of war."

The government dismisses the court and the allegations. Al-Bashir says more aid groups might be expelled if they overstep their mandate and insists the government can handle the situation.

But government workers in Darfur face a bigger challenge: refugee camp residents have little faith.

Gamila Youssef, 35 and a mother of three, said she rejects the government's offered hand.

"We don't want any health care from the government," she said. "They target us and then offer us health? How can that be?"