"We hope that he would be safe but we could not establish any contacts as the forest is dense and heavy rains are continuing in the area," said K Roshaiah, the state's finance minister.

'No attack'

The minister said the helicopter might have made an emergency landing because of the heavy rain.

Officials said they were worried about the ministers safety as there were many Maoist rebels in the district.

M K Narayanan, the national security advisor, ruled out the possibility of Maoists bringing down the helicopter, saying a technical snag or pilot error could have occurred.

"A Naxal [Maoist] strike seems extremely improbable. I would almost entirely rule it out," he said.

"I do not think the Naxalites have the capability to bring down the helicopter," Narayanan said in New Delhi, the national capital."

The Andhra Pradesh Aviation Corporation Limited (APACL) said it was highly probable the helicopter had made a safe landing in a remote area and said it had an emergency locator transmitter capable of automatic transmission in case of any crash landing

The National Remote Sensing Centre in Hyderabad, under the Indian Space Research Organisation, is flying a plane to photograph the forests in western Andhra Pradesh where the chief minister's helicopter went missing.