The official Sina Weibo account of the US Consulate General in Shanghai became "inaccessible" since Thursday morning for unknown reasons, a diplomat has told the Global Times.

"We discovered our Consulate Shanghai's official Sina Weibo page cannot be accessed since the opening hour of business at 8 am on Thursday morning. We're now trying to find out why," Wylita Bell, an information officer for the US Consulate General in Shanghai, said.

US diplomats have contacted the operator, Bell said. "Sina is very busy and we are still waiting for additional information."

Staff at Sina Weibo did not offer any explanation for the apparent malfunction.

Mao Taotao, a spokesman at Sina Weibo, declined to confirm whether the company had received calls from US officials as he claimed his unit was waiting for replies from the operator's technical department.

"We plan to resume normal operations as soon as possible," said a statement by the US Consulate General in Shanghai posted on its Tencent microblog account later on Thursday, which remained operational.

Sina Weibo accounts for US Consulate Generals in Guangzhou, Chengdu, Shenyang and Hong Kong still operated normally.

Shortly after the problem occurred with the Sina Weibo account of the US Consulate General in Shanghai, which has more than 80,000 followers, a number of accounts under similar names emerged, which confused some Web users.

"There is only one official account on Sina Weibo, which is now inaccessible," Bell told the Global Times.

In an entry in May, the US Consulate General in Hong Kong advised US diplomats in Shanghai not to repost an unidentified post. It could not be immediately verified what the information in the post related to.

Speculation appeared online suggesting that a post by the US Consulate General in Shanghai, which was responding to a Weibo user, "Shenzhen Laocui," who appeared to have ridiculed and challenged the findings of a fire accident in Tianjin, could have been one possible reason for the problem.

Officials said a department store fire in Jixian county in Tianjin on June 30 killed 10 people.  Police have punished several Web users for spreading rumors online exaggerating the death toll.

The speculation could not be confirmed by US diplomats on Thursday.

According to latest Sina regulations that took effect in May, any accounts that published more than five pieces of sensitive information that violate Chinese laws, contain rumors, or leak national secrets will be asked to delete the information and be punished by being barred from posting for over 48 hours. For those who maliciously post sensitive information, their accounts will be shut down.