Wildly popular in Europe since entering the continent's market in 2023, Temu said earlier this year it had on average around 75 million monthly active users in the bloc.

The European Commission, the EU's powerful digital watchdog, said it demanded Temu explain what measures have been taken to stop traders appearing and reappearing on the platform "selling illegal products".

The query was made under the EU's landmark law known as the Digital Services Act (DSA) that forces platforms to do more to protect consumers.

The EU also wants Temu to provide more data and information on actions taken to limit "risks relating to consumer protection, public health and users' wellbeing".

And Brussels demanded more details on Temu's recommender systems -- used to push more personalised content -- and the risk to the protection of users' personal data.

Temu must provide the information by October 21.

The latest demand is a first step but does not itself suggest the law has been broken, though it could lead to a formal probe culminating in fines if the violations are proven.

"Based on the assessment of Temu's replies, the Commission will determine the next steps," it said in a statement.

Temu said it was "fully cooperating" with the commission.

"In line with our longstanding commitment to compliance, we have taken further significant measures since (May)... and continue to refine our practices under the Digital Services Act," a Temu spokesperson said. "Consumer safety is a top priority."

The request for information is only the second for Temu after it was added to the EU's list of digital firms big enough to face greater curbs in May this year.

In June, the EU asked Temu to explain what action it was taking to protect consumers, including children, in its first set of questions.

The request included a demand to know how Temu was complying with rules regarding online interfaces to avoid "dark patterns", the practice of tricking users into making unwanted purchases or opting-in to certain settings without their knowledge.

European consumer groups in May lodged a complaint with the commission, accusing Temu of using "manipulative techniques" to make users spend more and other violations.

Six EU countries -- Austria, Denmark, France, Germany, The Netherlands and Poland -- urged Brussels for tighter supervision of Temu in September.