Government officials in a impoverished county in Central China's Hunan province are investigating a viral video that shows students pouring milk down a drain, news website The Paper reported Wednesday.

The video shows several children at a primary school in Longhui county squatting beside a gutter filled with leftover milk, which according to the school was still edible.

Longhui, a nationally designated impoverished county, provides free school meals to students.

The school's principal, identified only as Zeng, told The Paper that all leftover milk is thrown away due to fears the children will take it home and potentially drink it after the expiration date, which could make them sick.

Zeng said the rule was introduced after parents complained about their children drinking months-old milk. An investigation found some students had taken their milk home and allowed it to spoil, he added.

The principal denied the milk was poured away due to low quality.

Xiangmi Dairy, which produces the milk, came under scrutiny in 2016 when the company was omitted from a list of licensed suppliers issued by the Dairy Association of China, arousing parents' concern, according to media reports.

Some were also troubled to learn that it supplied more than 300 schools across Longhui.

In response, the county government issued a statement confirming that Xiangmi Dairy was licensed and qualified to provide schools with milk.

On Wednesday, the authority ordered a fresh investigation into potential problems with free meals to students.

The local education department has also been told to work with Xiangmi Dairy to "rectify problems, improve services and diversify services", while more effort should be made to help students and parents understand the free-meal policies, it said.

Xie Jianing contributed to this story.