Authorities lifted a partial ban on maritime traffic at a major northeast China port Tuesday, four days after explosions hit crude oil pipelines in Dalian, causing a lingering oil spill that has spread to tourist beaches.

The Maritime Affairs Administration of Liaoning Province reported that the ports in Dalian City have fully re-opened to traffic as of 5 p.m. Tuesday as waterways affected by the oil slick have been largely cleared for the resumption of shipping.

Authorities said they assisted about 420 vessels that were diverted to Dalian's ports during the past four days due to shipping restrictions brought on by the oil spill.

But local officials said oil shipments from Dalian, which lies at the heart of northeast China's crude oil production base and is considered the country's vital oil trans-shipment destination, would not be immediately restored.

Chinese petroleum companies' tankers have reduced oil shipments from Dalian to southern Chinese provinces while refineries roll back operations following the blasts and await the cleanup to be completed.

The incident began when two crude pipelines exploded last Friday evening in Xingang Port in northeast China's Dalian City. The blasts caused an oil slick, resulting in authorities rerouting maritime traffic during the cleanup.

The spill cleanup started Saturday. By Monday morning, 24 oil clean-up vessels and 800 fishing boats had collected about 460 tonnes of oil.

But the operations were forced to scale back on Tuesday due to strong winds and heavy rains. The State Oceanic Administration said late Tuesday that two of Dalian's famed beach resorts, including the state-level tourist beach Jinshitan, had been polluted by drifting oil.

The administration said its monitoring vessels could not conduct its daily oil spill survey on Tuesday because of the rough weather. According to Monday's survey, about 366 square kilometers of ocean were affected, including 52 square kilometers that were polluted and 12 square kilometers that were classified as "severely" polluted.

Dalian officials on Tuesday said they have mobilized forty special oil-skimming vessels and about 800 fishing boats to mop up the major oil slick by this weekend.

"Our priority is to collect the majority of the spilled oil within five days to reduce the possibility of contaminating international waters," Dai Yulin, vice mayor of Dalian City, Liaoning Province, told Xinhua on Tuesday.

Further, he said maritime agencies have set up 40 monitoring stations to watch a 1,500-square-kilometer area off the city's coast.

Maritime agencies and oil companies have laid down oil barriers of more than 15,000 meters to prevent the slick from spreading while biotechnicians are using 23 tonnes of oil-eating bacteria to dissolve toxic compounds in the oil-polluted waters.

Wu Jin, a PhD at the Institute of Microbiology at the Chinese Academy of Sciences, said oil-eating bacteria, unlike chemical oil-dispersants, can work 24 hours per day and are more environmental friendly.

Workers are concerned that the situation may worsen if the chemical oil-dispersant fail as winds continue to blow and rain continues to fall.

Jin Longsheng, a local fisherman whose boat remains docked on the polluted sea, said he was worried, since his fishing boat is too small to go far into the sea, that the oil spill might have driven away the marine life found close to shore.

"I don't know if I will be able to catch any fish when the fishing moratorium is over," he said. The fishing moratorium in Dalian is from June to August.

A resident along Dalian's coastal region, surnamed Sun, told Xinhua that the air in the city is has been uncomfortable to breathe since Monday, and smells like burned gasoline. However, the smell was lessened by Tuesday's rain.

Also, Wu Guogong, deputy director of the Environmental Protection Agency of Dalian, said local environmental authorities have set up dozens of water and air quality monitoring points, and so far the air quality will not a have significant impact on human health, according to the monitoring results.