QPR are reported to have offered £4.5 million for the former Scunthorpe forward, who has been the subject of failed bids from Norwich and Hull this year.
Manager Neil Lennon previously revealed Hooper had probably played his last game for the Glasgow club and the forward, who has been struggling with a groin strain, was absent as the Celtic squad flew to Belfast for their Champions League qualifier against Cliftonville.
"A bid came in last night," Mjallby said at Glasgow Airport. "I don't know how the club has responded to it.
"They increased the bid a wee bit when it came in yesterday. If it is good enough, I don't know. That's something you have to ask the chief executive, the manager and the board.
"We know it looks likely right now that Gary is going to leave the club. I'm not too sure the final word has been said yet. We have to wait and see.
"I think the club is going to sit down and think about it. If he has played his last game, I don't know."
Meanwhile QPR boss Harry Redknapp has ruled out a loan move for maverick midfielder Adel Taarabt.
Premier League new boys Hull have been linked with Taarabt, 24, but Redknapp insists the Moroccan will only be allowed to leave Loftus Road on a permanent transfer.
"What's the point in loaning him out for a year and then him coming back to us?" Redknapp told Sky Sports News.
"If he wants to go let somebody come and pay the money for him.
"If no one wants to buy him, he has to come and play here and do well and help QPR get back in the Premier League."
- Sports & Recreation
- Harry Redknapp