The death toll from an oil pipeline explosion in Shandong province's Qingdao city has reached 48, and another 136 were still hospitalized on Saturday.

The blast occurred at 10:30 am on Friday in Huangdao district, after crude oil leaked from a pipeline into the municipal pipe network. The accident's cause is still under investigation.

No one who made it to the hospital has died, local authorities said. The identities of the deceased have not yet been disclosed.

The pipeline leak began around 3 am on Friday, and it was shut down 15 minutes later.

Workers were repairing the pipeline when the blast occurred. The fire was put out at 1 pm.

About 18,000 people were evacuated from surrounding communities. The local government distributed 40,000 free breakfasts and lunches on Saturday.

Electricity has been restored in all communities in the district, the local government said.

Eight of the 136 hospitalized survivals have life-threatening injures, and 44 are in critical condition, according to a Qingdao public health bureau Web post.

Doctors have operated on 120 of the injured. Among them, 24 have received amputations or chest incisions to access organs, and 96 have had tissue removed or gotten sutures, the bureau said.

As of 3:30 Saturday afternoon, 556 people had donated 180 liters of blood for the injured.

There is enough blood, and no more donations are needed, the health bureau said on its micro blog.

Sixty-nine of the injured were hospitalized in the Affiliated Hospital of Qingdao University.

Six of the 69 have life-threatening injuries, the hospital's vice-president Liang Jun told China Daily.

"Teams of experts from the hospital and those dispatched by the National Health and Family Planning Commission and the provincial authorities have been established to offer follow-up treatments for the six," Liang said.

He said his hospital is mainly carrying out trauma operations, spleen removals and suturing on the others.

More than 100 medical experts and more than 200 nurses had been working nonstop for 28 hours to treat the injured as of 4 pm on Saturday afternoon, Liang said.

Liang said the hospital will initially pay the medical fees. It was not clear if the hospital would be reimbursed and, if so, by whom.

Xue Shumei is the oldest among the hospitalized. A door struck the 87-year-old in the head when she went to check the broken windows after the explosion.

"I'm very worried about similar accidents in the future," Xue's daughter said.

"I hope the government can find ways to prevent them."

The pipeline belongs to the country's largest oil refiner, China Petrochemical Corp, also known as Sinopec Group.

An early Xinhua News Agency report said the pipeline links oil depots in Huangdao with Weifang, also in Shandong province, and began operations in August. It was built with a total investment of 1.3 billion yuan ($210 million), the report said.

However, Sinopec Group denied the report on its micro blog on Saturday and said the leaking pipeline belongs to the Dong-Huang Line - flowing from Dongying, Shandong province, to Huangdao - not the Huang-Wei Line from Huangdao to Weifang.

The pipeline is 711 millimeters in diameter and runs 248.52 km, and began operating in July 1986, the company said. It has an annual oil-transfer capacity of 10 million metric tons.

The leaking crude oil flowed through the sewer into the ocean and polluted about 3,000 square meters of ocean.

The Qingdao Maritime Safety Administration said 3-km-long containment booms have been deployed. It said 40 tons of dispersant and 20 tons of oil-absorbent felt have been used.

A dam has also been built to contain the polluted seawater, and the crude oil has almost been cleaned from the ocean, local authorities said.

A total of 80 tons of oil-absorbent felt and oil-and-water mixture have been collected, the administration said.

The Qingdao environmental protection bureau said the blast has not noticeably affected air quality.

Sinopec's board chairman Fu Chengyu apologized for the accident on Saturday, according to the company's micro blog.

Fu said he grieves for the huge loss of life and property, and expressed deep condolences to the victims.

A woman surnamed Liang who works near the site told China Daily the air smelled acrid when she went outside after the blast.

"I saw heavy smoke in the sky and the street had collapsed," she said.