Paqueta has scored five goals in 42 West Ham appearances since arriving last yearLucas Paqueta is being investigated by the Football Association for potential betting rule breaches, sources have confirmed to the BBC.
The West Ham midfielder, 25, has been linked with a move to Manchester City.
On Friday, Paqueta was omitted from Brazil's squad for their upcoming World Cup qualifiers "for him to sort out his problems".
Sky Sports reportedexternal-link Paqueta as saying he had not placed any bets himself and was shocked by the reports.
The investigation, which is also said to involve world governing body Fifa, is believed to centre around bets placed in Brazil on yellow cards awarded against Paqueta.
Speaking on Friday, Brazil's interim coach Fernando Diniz said Paqueta had been left out of his squad for qualifiers against Bolivia and Peru next month.
"Paqueta was on the list, he's a player I like a lot. It's a time for him to resolve these issues," Diniz told reporters.
"People need time to sort these issues out. He's a player I love, I have the best impressions of him."
BBC Sport has approached the FA and West Ham for comment.
Paqueta joined the Hammers from Lyon for £36.5m last summer and was instrumental in the club winning the Europa Conference League.
He made 28 Premier League appearances last season, scoring four goals and assisting three.
City boss Pep Guardiola said in a news conference on Friday that Paqueta "is a West Ham player" and would not comment on a potential transfer.
In May, Brentford forward Ivan Toney was suspended from football for eight months for 232 breaches of the FA's betting rules.
