(AFP) The search for a German research student who disappeared mysteriously in a jungle monkey sanctuary in Sabah a week ago was joined today by his sister and a German diplomat.

Arne Lennart Cornelius, 21, of Bremen, was last seen with his guide as they entered the 300-hectare Labuk Bay Proboscis Monkey Sanctuary last Thursday.

Several villagers, however, claim to have seen the guide, Joseph Mohamad Faisal, also 21, emerging from the jungle the same day, police say.

Cornelius's sister Alva arrived in Sabah today and was taken straight to the sanctuary. She declined to speak to reporters.

German diplomat Gabriele Kowal Manderla also flew in to Sabah from the embassy in Kuala Lumpur and went to the park to meet police and rescue teams.

"We want to thank the search and rescue teams who have been really helpful and committed in searching for Arne," she said.

Helping hand

The diplomat also extended an offer by the embassy to assist police in search operations.

Scores of police with tracker dogs have been combing the jungle since Cornelius failed to return from what was supposed to be a one-day field trip.

They are also searching the Semawang River, which passes through the sanctuary, located some 30 kilometres from Sandakan.

"The search will be carried on until we find him," district police chief Hashim Mohamad Yusof told AFP .

Hashim said police had interviewed the villagers who said they had seen the guide leave the sanctuary and were compiling results of the investigations, which were still based on a "missing persons" report.

Cornelius, who arrived here on August 2, had been researching proboscis monkeys in the private sanctuary which was opened to the public three months ago.