The police today arrested social activist Medha Patkar who participated in a march here in protest against farmland acquisition for Tata Motors' project at Singur.Patkar and CPI-ML leaders were part of a silent procession with their mouths tied with black cloth.The police, however, did not say immediately why Patkar was taken into custody. Tension prevailed in the area after her arrest.Patkar, who had reached Singur last Saturday when violence broke out there in protest against land acquisition, was detained at that time. Subsequently, she was not allowed to go to Singur despite many efforts.Meanwhile, Trinamool Congress general secretary Mukul Roy said that Mamata Banerjee "is not keeping well, but she is in good spirit". She would continue the hunger strike till the government met the demands, he said.Banerjee had said yesterday that her head was reeling, but continued her fast despite an appeal by Chief Minister Buddhadeb Bhattacharjee yesterday to call it off.Litterateur Mahasweta Devi today condemned the arrest of Medha Patkar, and demanded her immediate release by the Buddhadev Bhattacharjee government.