JOHANNESBURG, South Africa — Eleven nightshift workers allegedly locked into a Johannesburg chemical factory to prevent them from stealing burned to death early Saturday, police said.

Superintendent Richard Luvhengo said the 10 women and their male supervisor appeared to have tried to break open a padlocked door. Police were investigating possible charges of murder or culpable homicide against the owner.

"You can see from where they died that they tried to hide from the fire in another part of the factory. It seems to indicate that they knew they could not get out," he said.

Forensic experts had examined the ruins of the factory and concluded that the fire could have been caused by chemicals unlawfully stored at the site, Luvhengo said. The factory owner was remaining silent on the advice of his lawyers.

"He has not yet been arrested, but if the forensic guys confirm what they are saying today he will be. " Luvhengo continued.

Margaret Washington told Reuters that she and her best friend, Rachel, had planned to quit their job mixing floor polish at the Esschem factory in Lenasia, a suburb south of Johannesburg. Washington stayed home on Friday night because of pain from an old burn wound on her leg.

On Saturday, she stood in the rain with stunned day-shift workers and relatives watching police pull small, charred shapes from the rubble of the factory.

One of them was Rachel, but it was impossible to tell which.

"I pray to God to save my life because I am supposed to be dead now," she said, adding that she had worked for 175 rand ($23.30) every two weeks.

Washington confirmed claims by bystanders that the owner of the factory, who was present but declined to give his name, had routinely locked nightshift workers in because he was afraid they would steal from his stores.

"It is true," she told Reuters.

Luvhengo said gas bottles used for heating chemicals appeared to have exploded, but it was not immediately clear whether they caused the fire or exploded in the flames.

"By the end of the day we had been able to take out nine bodies. We will get the other two tomorrow."

He said people tried to rescue the workers from the flames, but they could not reach them.

"Witnesses are saying they came from a nightclub that is near here and that they could hear the people screaming, but they could not get in because the gates and the doors were locked," he said.

Firemen had to cut locks on the outer security fence of the factory and entered the building through a hole apparently blown in the wall. The main entrance was still padlocked on Saturday.

Officials on the scene said some of the bodies had become stuck in melted plastic from large tanks holding chemicals. One woman appeared to have suffocated and others probably died under piles of brick and debris left by the explosion of gas bottles inside the factory.

"The fire brigade put out the fire early today, but it was too dark to start looking for the bodies of the victims. We came back to it at seven this morning," Luvhengo said.

In another incident, police reported a married couple and their four children burned to death in a shanty in Northern Province, apparently after a neighbor poured petrol over their home and set it alight. A police spokesman said the neighbor, who was facing assault charges laid by one of his victims, had been arrested.