Shannu Khatun, in her mid-30s, who was struggling for survival, sold her son to a Nepalese couple at Forbesganj railway station, near the Indo-Nepal border in Araria, about 350 km from here.

"Khatun has disappeared from the railway station, police have been trying to trace her whereabouts," Araria Superintendent of police Shivdeep W. Lande said.

Nitish Kumar Monday told media persons here that it was a serious matter and the government will act in this case. "The government will take action in this matter," he said.

Lande said that he has directed the local police and approached the Railway Protection Force to look for Khatun. "She may be hiding, fearing police action. But police are keen to help her to recover of her sold child," Lande said.

"Police have been investigating," he added.

According to district police officials, a police team returned empty handed from her village as she was not found there.

Khatun, along with her children, left her village a few days ago and took shelter at the Forbesganj railway station. She denied she had sold her child, but admitted to giving it away for his own sake.

Police officials suspect that Khatun was forced to leave the railway station by the RPF and railway authorities in view of the embarrassment caused to them by the incident.

But her eight-year-old elder daughter Sabina told some local residents that her mother sold her younger brother for a mere Nepalese Rs.100 (Indian Rs.62).

Earlier, Syed Ahsan Ali of the Railway Protection Force said Khatun had "donated" her child to a Nepalese couple. "She told us that she had not received any money for it."

Opposition Rashtriya Janata Dal (RJD), Lok Janshakti Party (LJP), Congress and Left parties said that Khatun's case has exposed Chief Minister Nitish Kumar's much publicised development and good governance claims.

"What type of development it is when a poverty stricken woman is forced to sell her child for few rupees?" RJD leader Ram Kirpal Yadav said.