The Shanghai Wildlife Protection Office has still not discovered the source of two young estuarine crocodiles found in the city recently.

Investigation of nearby restaurants came up with nothing, officials said.Officers  visited the Lantian Hotel in Yangpu District on Wednesday, the only restaurant big enough to deal with crocodile meat near the Wujiaochang area of Yangpu District, where an estuarine crocodile was found on a Metro Line 10 construction site Tuesday.

They found no clue in the kitchen or store house.

"We had no evidence proving that they were doing crocodile trade," said Pei Enle, director of the office. "So we couldn't take any action, but only warned the hotel that it's illegal to sell crocodile without the government's permission."

Pei said estuarine crocodiles are endangered.

"Most wild estuarine crocodiles live in Southeast Asia," he said. "The two crocodiles may come from abroad. They managed to escape on the way to restaurants."

According to Pei, the office has uncovered six cases of illegal trading of estuarine crocodiles in the first half of this year, most involving the restaurant industry. "It's legal to raise edible crocodile if you have a certificate from the government," Pei said, "but smuggling wild crocodiles is illegal."

The two crocodiles have found a new home at Shanghai Zoo. After brief treatment, the crocodiles' condition has stabilized but they still need about 10 days to fully recover.

Both crocodiles had mouth abscesses because their snouts were taped for more than a week.

"No fresh air could go into their mouths so they started to canker," said Wu Weichun, director of zoo's amphibian department.

The other crocodile was spotted on the A30 highway in Qingpu District July 25. They were both in their childhood.

"The two crocodiles had seals on their mouth of different color and material," Wu said. "Thus we could not confirm whether they came from the same source."

Late last year, an estuarine crocodile was found in a primary school's pool in Minhang District, terrifying both pupils and teachers.

The crocodile was also ended up at the zoo.