The Shanghai Blood Administration Office reiterated that residents can't be paid for blood donations Tuesday after a microblogger posted a photo of a flier offering 900 yuan ($143) for a donation.

The office, which manages the city's blood supply, responded by encouraging residents to voluntarily donate their blood at official collection points or to participate in voluntary blood drives organized by their employers, according to a press release.

 The press release followed a post on Sina Weibo early Tuesday morning that showed a letter-sized black and white flier that offered cash for a 400-milliliter blood donation. The post had been forwarded more than 500 times by Tuesday evening.

The flier appeared Friday in the poster's building in a residential community on Nanning Road in Xuhui district, according to the poster, who asked to remain anonymous. The poster said he has reported the flier to police.

The Shanghai municipal government reminded residents not to be fooled by such advertisements, according to a post on its official microblog.

The Shanghai Blood Administration Office has received several reports about money being offered for blood donations, a staff member said. To maintain the city's blood supply, many companies are given an annual blood donation quota that they fill by sending employees to voluntarily donate blood.

"Along with individual donors on the street, this is a crucial source for our blood bank," she told the Global Times. "However, there are a few employers who cannot meet their quota and have to pay people to donate blood."

With the increasing demand for blood, the problem could get worse, the staff member said.

"We predict that about 520,000 patients will need blood transfusions in 2016, but we are not optimistic that we will be able to beat last year's number of 460,000 donors to meet that requirement. We may have to rely more heavily on group donations," she told the Global Times.