HONG KONG — A municipal government in southwestern China has suspended at least temporarily the construction of a metals factory after bloody street protests on Monday, in the latest sign of the growing strength of the country’s environmental movement.

The police in Shifang, an ancient city in Sichuan Province that suffered heavy damage during a 2008 earthquake, issued a warning on Tuesday that they would “severely punish” anyone involved in further protests. Yet postings on Chinese social media said that thousands gathered outside local government offices again on Tuesday night to demand the release of students detained in the previous day’s protests; it was not immediately clear how the police would respond.

The municipal government said in a separate statement that it had opened a special phone line and e-mail account to answer questions about the $1.7 billion project and promote a “correct understanding” of it — steps that seemed to suggest that construction might resume in the future.