Relief workers reported the first signs of disease Wednesday among survivors of a devastating earthquake and tsunami in the Solomon Islands, while aftershocks hampered efforts to get aid to survivors running low on food and water.

Some children in makeshift camps that have sprung up in hills behind towns hit by Monday's disaster have diarrhea, the Red Cross said, as threats such as malaria, dysentery and cholera loomed.

Survivors terrified by the more than 50 jolts that have struck the region since the magnitude 8.1 quake — including several registering 6 or stronger — were too scared to come down from high-ground refuges, officials said, adding to difficulties assessing the number of victims and getting aid to survivors.

"There's no water to wash, no water to drink," said Esther Zekele, who fled with her husband and five children to the hills behind Munda on Monday as the sea surged through the town. About 40 other families were also huddled at their makeshift camp.

They ventured back home on Wednesday, hoping to replenish their half-eaten bag of rice, but took to the hills again when they heard a rumor another wave was coming.

Now the families are just waiting, wondering why help hasn't come, Zekele said.

Solomon's deputy police commissioner, Peter Marshall, said the aftershocks had pushed some survivors even deeper into the hills.

"People are in a panic because of the continuous tremors," said Rex Tara, a disaster management specialist with British-based aid agency Oxfam.

At least 28 people were killed, and authorities were checking unconfirmed reports of further deaths, including six people buried in a quake-triggered landslide on Simbo island, Prime Minister Manasseh Sogavare's office said.

Marshall said that while the death toll may continue to rise, aerial surveillance flights over the past two days had revealed "no evidence of mass deaths."

Authorities had no firm figure for the missing.

Red Cross official Nancy Jolo said her agency had handed out all the emergency supplies it had stored in Gizo, the main town in the disaster zone, and was waiting for new supplies from a New Zealand military transport plane that landed late Tuesday in Munda.

"The priority need right now is for water," Jolo told Australian Broadcasting Corp. radio. "What we are experiencing right now in some of the campsites is children starting to experience diarrhea."

Six doctors and 15 nurses from Honiara were among aid workers who arrived Wednesday at Gizo, where plans to reopen the airport the same day didn't pan out and the wharf remained badly damaged.

Many of the 5,600 left homeless were scrounging for basic supplies under buildings knocked down by the quake and sludge deposited by the tsunami.

One police patrol boat arrived in Gizo on Tuesday after traveling 10 hours from the capital, Honiara, with tents, tarps, food and water. A second supply boat left Honiara on Wednesday evening, but two others were delayed because provisions could not be found to fill them, chief government spokesman Alfred Maesulia said.

"It's very difficult to get the materials needed because Honiara only has very small shops," he said.

A New Zealand military transport plane unloaded a shipment of tarps, water and rations at Munda.

"We have not reached people as soon as we could ... because of the widespread nature of this particular disaster," said Fred Fakarii, chairman of the National Disaster Management Council.

Many canoes and other boats were sunk or washed away by the tsunami and fuel was contaminated with sea water, adding to the aid delivery woes, Western Province Premier Alex Lokopio said.

Fakarii said officials had asked for two mobile hospitals from Australia and New Zealand. Hospitals at Gizo and Munda were wrecked by the disaster, he said.

The quake, which struck 6 miles under the sea about 25 miles from Gizo, set off alarms from Tokyo to Hawaii, testing procedures put in place after the2004 Indian Ocean tsunami that left 230,000 dead or missing in a dozen countries.

Gizo's proximity to the epicenter meant the destructive waves — up to 16 feet high — hit before an alarm could be sounded, rekindling debate about whether the multimillion-dollar warning systems installed after the 2004 tsunami are worth the cost.

No significant tsunami was reported Monday anywhere outside the Solomons, which are comprised of more than 200 islands with a population of about 552,000 people.