HONG KONG (Reuters) - A young clerk with no knowledge of the 1989 Tiananmen Square crackdown allowed a tribute to victims slip into the classified ads page of a newspaper in southwest China, a Hong Kong daily reported on Wednesday.

The tiny ad in the lower right corner of page 14 of the Chengdu Evening News on Monday night, read: “Paying tribute to the strong(-willed) mothers of June 4 victims”.

An investigation was launched by Chinese authorities to find out how the advertisement slipped its way past censors.

Public discussion of the massacre is still taboo in Beijing and the government has rejected calls to overturn the verdict that the student-led demonstrations were “counter-revolutionary”, or subversive. Hundreds, perhaps thousands, were killed when the army crushed the pro-democracy protests on June 4, 1989.

Hong Kong’s South China Morning Post said a young woman on the Chengdu Evening News classified section had allowed the ad to be published because she’d never heard of the June 4 crackdown.

A man gave the advertisement to the clerk, who had recently graduated and worked for an advertising company responsible for receiving content for the ads section, the Post reported.

“She called the man back two days later to check what June 4 meant and the man said it was (a date on which) a mining disaster took place,” the Post quoted a source at the paper as saying.

“This highlights (the fact) that the government needs to face up to history,” the paper quoted the source as saying.

References to the massacre are barred in state media, the Internet and printed works, meaning many of China’s younger generation are ignorant of the events.