SAO PAULO, July 20 (Reuters) - Brazil's securities regulator CVM said on Monday it had opened a preliminary investigation into Via Varejo SA after a series of posts were sent from the retailer's Twitter account purporting to show strong May and June sales data.

Via Varejo said in one of the Twitter postings that game and camera sales had skyrocketed 2,500% in May and June from a year earlier. Another tweet claimed its TV sales had soared 1,900% amid the coronavirus pandemic. But the tweets were later deleted from Via Varejo's account.

The postings helped trigger a 7.35% rally in Via Varejo shares on Monday as the once troubled retailer outperformed e-commerce-focused rivals such as Magazine Luiza SA and B2W.

CVM said in a statement that companies are allowed to release information on social media platforms as long as they also send it to the regulator. CVM added the information published on social media also must be correct.

Via Varejo did not immediately comment on the matter.

(Reporting by Alberto Alerigi and Paula Laier, writing by Carolina Mandl Editing by Marguerita Choy)