By Omer Farooq BBC correspondent in Hyderabad

The southern Indian state of Andhra Pradesh is slowly trying to restore normal life after a killer heat wave that has claimed more than 600 lives.

It was so bad that birds fell dead from trees

West Godavari district administrator

Heavy showers since Thursday have begun lowering temperatures from the searing highs of 50C suffered by many parts of the state.

Chief Minister Chandrababu Naidu described the tragedy as unprecedented in the region's history.

He has asked the central government in Delhi for emergency assistance and help with medical relief for the affected areas in his state.

But as the state begins the slow process of recovery, many are asking how so many could have died.

Extremes

"It was so bad that birds fell dead from trees," said Ponnam Malkondaiah, chief of administration for West Godavari district where 45 people died.

Few heat waves in the past have lasted as long as the latest one, which went on for a week, or risen to such extremes.

Mr Malkondaiah said his district saw temperatures as high as 51C, against previous highs of 45C.

RP Meena, the district collector in Krishna, where 102 people died, said it was the old who were the most vulnerable.

"We had a 115-year-old man and a 92-year-old man dying of heat. They were not able to withstand this temperature," he said.

Mr Meena said the people of Andhra Pradesh were simply not used to such temperatures, and therefore unable to withstand them.

Dr Raghunath Reddy, who dealt with some of the heat wave cases in Warangal district, where 45 people died, said many succumbed to dehydration.

"Many people came in at the end stage where it was very difficult to save them," he said.

But doctors also said that sunstroke was not the sole cause of death.

"In many cases the heat wave only accentuated existing ailments and people succumbed unable to bear the impact of the heat wave," said Dr Gopalakrishna of Eluru district.

Natural cycle

But environmental factors were also to blame.

"The heat was aggravated by the absence of shadowy trees which can give shelter to the people and lessen the impact of the heat wave," said R Rajamani, former government secretary for forests and environment and a prominent environmental activist.

Environmental degradation compounded the disaster

He said declining water levels in lakes in the state had also added to the tragedy.

"But the entire problem of heat waves cannot be blamed on man-made causes. It is a natural cycle. The heat wave has its own role to play in inducing moisture and rains".

But some problems definitely are man-made.

The state government has offered 50,000 rupees ($1,000) in compensation to the family of every victim.

But because many families did not lodge a first information report with the police or organise an autopsy, they are unlikely to get compensation.