Visa services have been suspended at the US consulate in Guangzhou, capital of Guangdong province, after it received a bag of unidentified white powder on Monday.

"Visa services will only resume once the incident has been fully investigated," a spokesman for the consulate said on Tuesday on condition of anonymity.

"The source and identity of the unidentified material is now under police investigation," the official added.

He said there had been no reports of anyone being adversely affected by the powder.

An envelope packed with the unidentified white powder arrived at the consulate's visa department, on the city's busy Linhezhong Road, near Guangzhou East Railway Station in Tianhe district, on Monday morning.

The material was scattered on the clothes of a visa department official after the package was opened.

The department immediately suspended visa services, cleared the visa hall, and launched an investigation, said the spokesman.

Anyone with a visa interview on Monday and Tuesday is being asked to arrange a new time with the visa services department.

Guangzhou police refused to comment on the incident.

Hualu Holiday, a travel agency in Guangzhou, posted a notice on its micro blog informing customers about the unexpected closure of the visa department.

An employee at the agency, surnamed Lu, said four of its customers had been affected by the suspension of services.

"All of them are worried the delay will affect their visits," she said.

A middle school student in Guangdong's Chaozhou city, who is applying for a summer camp in the US, told China Daily she had traveled to Guangzhou especially for her visa.

"I am so frustrated. I got there only to find the visa department was closed. I will have to ask for leave and fly to Guangzhou from Chaozhou again next week," she said.

Nolan Barkhouse, a spokesman for the US embassy in Beijing, said the embassy and consulates in other Chinese cities, are not affected by the issue. "The visa services of our consulates in other cities remain open."

There are US consulates in Chengdu, Shenyang, Guangzhou, Shanghai and Wuhan.

The Guangzhou consulate deals with visa applications from Guangdong, Fujian and Hainan provinces and the Guangxi Zhuang autonomous region, as well as nationwide immigration visa applications.

Feng Minghui and Cao Xiating contributed to this story.