Updated

A new calamity emerged Tuesday in the flood-hit Balkans as rescue workers battled overflowing rivers: tons of drowned livestock posing a health hazard.

With the rainfall stopping and temperatures rising, the withdrawing floodwaters revealed a harrowing sight: thousands of dead cows, pigs, sheep, dogs and other animals left behind as their panicked owners fled rapidly advancing torrents.

"There are tons of dead animals that we must dispose of," Serbian Prime Minister Aleksandar Vucic told a government meeting Tuesday.

In the northern Bosnian town of Samac, troops were using ropes to pull nearly 400 dead cows out of a barn and driving the carcasses away on trucks. In Samac, like many Bosnian and Serbian towns, waters rose within hours, racing into yards and homes without warning. Farmers did not always have time to unleash their livestock or let them out of barns to try to swim to safety.

Some dead animals were still hanging over the metal fences they tried to jump over when the water rushed in.

"Dead animals are a special problem and those have to be removed and destroyed properly," said Bosnia's chief epidemiologist, Dr. Zeljko Ler.

Chief Serbian Veterinary Inspector Sanja Celbicanin said 140 tons of drowned animals have been destroyed so far but much more work lay ahead. Some 1,900 sheep and lambs died in just one area of central Serbia alone and teams can only work in areas that police have deemed safe, she said, urging residents not to touch the dead animals.

Serbian state television showed army teams spreading out Tuesday to decontaminate and disinfect flooded areas to prevent possible diseases.

Residents in both countries were told not to return to their homes before teams disinfect the area and not to eat any food from flooded gardens, orchards or barns.

Ler warned that acute stomach ailments and other diseases — including hepatitis and typhoid — often occur after flooding.

"We are warning the population to drink only boiled or bottled water," he said. "There are still no mass infections (yet) but for some diseases the incubation period is 14 to 21 days."

The record flooding in Bosnia, Serbia and Croatia in past week has forced half a million people out of their homes and led to at least 43 deaths: 20 in Serbia, 21 in Bosnia and two in Croatia. Authorities say the death toll still could go higher.

Bosnia declared Tuesday a day of mourning while Serbia said it would hold three days of mourning from Wednesday to Friday.

In villages and towns along the Sava River, which forms the border between Bosnia and Croatia, water was still over one meter (yard) high Tuesday. Volunteers were still evacuating people and distributing aid to those who decided to wait out the flood on higher floors. The flooding was still threatening Serbia's biggest power plant in the hard-hit town of Obrenovac.

Water levels in the mighty Danube were also rising Tuesday, prompting Serbian authorities to order the evacuation of two villages along Europe's second-largest river.

In Bosnia, army helicopters dropped iron bars onto collapsed river barriers for the second day, aiming to later drop sandbags on them to try to close the gaps. Many areas faced land mine dangers after thousands of landslides hit, shifting mine fields left over from the country's 1992-95 war.

Bosnia's presidency said it will organize an international donor's conference and asked commercial banks to reprogram the mortgages of those who had lost property in the flooding.