Supporters said they hoped Theresa McDermott, 43, may be released today as the Israeli authorities continue their deportation of the hundreds of international activists detained in the raid on the aid flotilla in which nine people were killed.
One activist, Hasan Nowarah from Bearsden, who arrived back in Scotland last night, said he believed Ms McDermott, a postal worker from Pilrig, had been badly beaten up.
Carl Abernethy, who founded Free Gaza-Scotland along with Ms McDermott last year, said he had no information that she had been beaten.
He said: "We know she is being held in the Beersheba jail, but they seem to want rid of everyone as quickly as possible.
"It would be fantastic if Theresa were released today so we can find out how she is and she can tell us exactly what happened."
Ms McDermott was aboard the Challenger 1 passenger boat that was running alongside Turkish ship Mavi Marmara when it was boarded by gun-toting Israeli troops. Challenger 1 was taken without a fight.
Earlier reports suggested that she may have boarded MV Rachel Corrie, a converted Irish merchant ship which was held up by technical problems and may still be attempting to reach Gaza. The news that Ms McDermott was not on the Rachel Corrie came as a relief to her sister Winnie Chambers, but she is still awaiting news of her condition in prison and how she is being treated.
She said: "We have heard nothing from the Foreign Office. Our brother has been going through various official channels looking for information.
"We weren't sure if she had transferred on to the Rachel Corrie without telling us.
"It's the kind of thing she would do.
"I know she was due to set sail from Crete to Cyprus to pick up some Irish MPs, a couple of German politicians, and a girl called Alex, before setting off to Gaza.
"The last thing she said was that the passengers probably had more to fear from her cooking than they did from the Israelis."
Edinburgh North & Leith Labour MP Mark Lazarowicz said he had contacted Foreign Secretary William Hague, urging him to demand Ms McDermott's immediate release from Israeli custody.
He said: "This tragedy once again underlines the need for an end to the blockade of Gaza - the ships were carrying medical supplies and schoolbooks not guns and rockets."