A Beijing subway tunnel collapse that killed at least five workers last week has shown up management deficiencies in China's construction sector and aroused new concerns about the safety of migrant workers.

After retrieving the bodies of five of the six workers who were trapped when the Beijing subway tunnel collapsed at 9:30 a.m. last Wednesday, rescuers decided to halt the rescue work on safety grounds.

The fifth body was found at around 8:00 p.m. on Sunday and rescuers had expected to recover the sixth on Monday. But they found no sign of life in the rubble after a thorough investigation with high-tech probing devices and sniffer dogs, emergency rescue headquarters said on Monday.

It is now six days since the cave-in occurred last Wednesday at a construction site on the No. 10 Subway Line in Haidian Nanlu Road between the northern third and fourth Ring Roads in Haidian District, northwest of Beijing, and there is virtually no hope for the last victim.

The No. 10 subway line runs east to west above the Third Ring, through Zhongguancun high-tech zone in the northwest and the diplomatic areas in the east and will connect to a separate line running directly to the Olympic Village north of Beijing when completed in 2008.

"The underground situation is complicated and risks of further cave-ins threaten rescuers' lives, so we have decided to continue the search for the sixth body after construction resumes at the site," emergency rescue headquarters said in a statement.

The accident was the fifth on the No. 10 subway line since construction began in 2005, Hubei TV said on its website.

Investigators say the construction site is prone to cave-ins because it used to be a pond surrounded by graves and cropland and was loosely filled with sand in the 1950s.

China Railway 12th Bureau Group Co. initially failed to report the accident to municipal authorities and mounted its own rescue operation instead.

In an alleged cover-up attempt, project managers ordered all workers to stay at the construction site and not to talk to the media or police. They also confiscated most of the workers' cell phones.

The Beijing municipal authority learned of the accident at 5:00 p.m. on Wednesday, almost eight hours after the collapse, after a worker from central Henan Province called his family, who then sought help from police in their hometown.

Rescuers recovered the first body late Friday afternoon and four others on Sunday.

The victims include 20-year-old Li Peng from Henan and four from southwestern Sichuan Province. They were all from poverty-stricken families and were eking out their lives in Beijing. The youngest, Zhou Jie from Danling County in Sichuan, was 18. His uncle Zhou Yongquan is the worker still missing.

Family members of the six workers arrived in Beijing over the weekend.

Zhou Jie's father arrived in Beijing last Friday, but could only wait at a hotel for information about his son and brother.

"I don't know what happened to them," said the elderly Zhou. "I know the rescuers are working around the clock, but I have had no chance to go to the site since arriving in Beijing."

"Sichuan and Beijing officials are very concerned and two government officials from our county have also come to Beijing," he said.

He said the construction company -- China Railway 12th Bureau Group Co.-- had been taking care of the victims' families since they came to Beijing, but the company had not talked about compensation.

"If the way they deal with the aftermath is not satisfactory, I may go to court," said Zhou.

Liao Zhengjun, a 37-year-old victim from Ya'an in Sichuan Province, had been in Beijing for only four weeks. Liao lost his mother at the age of two and remained a bachelor all his life. When news of his death reached his 70-year-old father, the old man was still toiling in the fields. "With my son gone, I have to work even harder," he told reporters who interviewed him on Sunday.

Police have detained 10 people in connection with the cave-in, including the site supervisor and tunnel designers.

The accident has raised public concern about the rights and safety of migrant workers, many of whom do the dirtiest and most dangerous jobs but are often underpaid.

"We work 12 hours a day but are rarely paid overtime," said Wang Wenshan, a construction worker at the same construction site.

Wang said the tunnel collapse could have been foreseen. "On Tuesday, the day before the accident, our co-worker Old Zhang saw cracks in the newly excavated tunnel more than 10 meters underground. He reported to his boss but was told to go ahead."

Their boss Zhou Yongfu was one of two subcontractors for the project and had hired more than 60 temporary workers from Sichuan, he said.