Heavy rains forced rescuers to stop searching Thursday for more than 500 people feared dead after an overcrowded ferry sank in southern Bangladesh (search).

Crews still haven't even found the ferry MV Nasreen (search), which went down Tuesday night with 750 people aboard and is believed to be under about 200 feet of water.

"We have not been able to determine where the ferry is. Locating the ferry is our first job before any salvage operation can start," said Abdur Rab Howlader (search), a regional government administrator.

Hundreds of relatives lined the shore desperate to locate loved ones, while others raised black flags of mourning over their village homes.

Rescue officials said 220 people survived and only four bodies had been found. The exact number of passengers was unclear because ferries do not carry passenger lists and many people buy tickets when on board.

Dhaka's Ittefaq newspaper reported the ferry was carrying more than 1,000 people. Many passengers were sleeping and feared trapped inside the ferry when it sank.

"I shall not leave this place until I find my son," cried Khaleda Akthar, a 25-year-old woman who had been on the top deck but was missing her 5-month-old son Bacchu.

Akthar was traveling from Dhaka where she works in a garment factory to her village home in the Bhola district when it sank. "My relatives wanted to see my baby," she said.

The ferry, which had a capacity for only 350 people, sank where three flood-swollen rivers, the Padma, Meghna and Dakatia, meet in Chandpur, 64 miles southeast of Dhaka.

Choppy waters washed dolls, shoes, dresses, suitcases and other belongings ashore.

Two salvage ships were trying to locate the sunken ferry. The ships are equipped with cranes to pull the ferry up from the river bed.

Authorities also called in navy divers to help with the salvage work.

Heavy monsoon rains have swollen many rivers in Bangladesh, which has been hit by floods in the past two weeks that have killed at least 95 people.

Frequent boating accidents claim hundreds of lives every year in this delta nation of 130 million people. They are often blamed on overloading, faulty construction and disregard for safety measures.

In April, following protests by boat operators, Bangladesh officials withdrew a ban on night travel by ferries that was instituted after a series of accidents.

In return for the lifting of the ban, ferry owners promised not to operate their vessels in inclement weather and to follow safety regulations.

Two river ferries went down on April 21 in separate accidents near Dhaka, killing more than 135 people.