Guwahati, Oct 22 : Police are clueless a week after P. Krishna Rao, a civil engineer from Andhra Pradesh, was kidnapped by tribal separatists from a national highway construction site in Assam. The infrastructure firm he works for Thursday appealed for his release.

Officials of Gayatri Company pleaded with the abductors to release Rao on humanitarian grounds.

"We appeal to those who kidnapped Rao to please release him as he is on constant medication and has a family back home in Andhra Pradesh," S. N. Raju, deputy general manager of Gayatri Company, told journalists.

But there is no news of him so far.

"We are continuing with our search operation although we have not been able to rescue him," a senior Assam police official said on condition of anonymity.

Rao, from Gannavaram in the coastal district of Krishna in Andhra Pradesh, was kidnapped by suspected militants of the outlawed National Democratic Front of Bodoland (NDFB) from a highway construction site near Joypur in Kokrajhar district, about 230 km west of Assam's main city of Guwahati.

He was the project manager of Gayatri Company, a private infrastructure firm engaged in constructing a four-lane highway in a 63-km strip in the district.

The Assam government had earlier announced the setting up of a Special Task Force for rescuing the abducted engineer. "We have already launched a massive hunt to rescue the abducted engineer," the official said. (IANS)