Striker Folan, who last scored on the opening day of last season, has started all four of the club's Premier League games to date but has been left out of the 20-man squad for the game at Sunderland on Sunday.
Brown: "Championship clubs are beckoning for maybe four or five of our players and maybe some need to go out on loan.
"There's been an enquiry for Caleb from Middlesbrough and also an enquiry from Newcastle.
"I've spoken to (Boro boss) Gareth Southgate on two or three occasions and now we're leaving it to the business men to draft a deal.
"We've also had an enquiry from Reading for Bryan Hughes and for Daniel Cousin from Newcastle. We've had a number of enquiries about players who are not in the squad, that's football."