Nora Quoirin went missing on Sunday morning after checking in with her family to the Dusun Resort, about an hour from the capital Kuala Lumpur. Family members said they found the window of her room open in the morning without any trace of her.
The 15-year-old lives in London and is the daughter of a Franco-Irish couple.
Her family suspect foul play, but the Malaysian government has stressed police do not believe she was abducted and are calling for an end to speculation about her disappearance.
As the hunt entered a fourth day Wednesday, a small team of divers searched a river running through the forest near the resort, AFP journalists at the scene said.
A helicopter, two drones, sniffer dogs and 214 people from various government agencies had already been deployed in the hunt for the girl.
A Malaysian diver takes part in the search and rescue operation
Che Zakaria Othman, deputy police chief of Negeri Sembilan state where the resort is located, said around 20 witnesses, including family members, had been interviewed.
Forensics experts were also able to take fingerprints from the window panel of the girl's bedroom but did not say who they belonged to, he told reporters in the state capital Seremban.
"We are not ruling out any possibilities but so far we don't have any information," he added.
"We still believe she is in the area because there is no information that says she has left."
Police have classified her disappearance as a missing person case, but her grandfather, Sylvain Quoirin, told AFP Tuesday that she had gone in "extremely mysterious" circumstances and was not in the habit of running off.
"In the morning, the window was open and she had disappeared," Quoirin said by phone from Venisy, in north-central France where he is the mayor.
"After an 18-hour flight and a seven-hour time difference you would sleep soundly and not go for a stroll at night," he said.
The family had planned to stay for two weeks, he said, and Nora was "absolutely not" in the habit of running off.
Malaysian Home Minister Muhyiddin Yassin, however, said police do not believe anyone else was involved.
"What other people say is not important because the police know better," he was cited as saying by official news agency Bernama. "Everyone who comes to our country is safe and does not face problems."
The Dusun is a 12-acre (five-hectare) resort in the foothills of a mountain range and next to a forest reserve.
The resort's management said in a Facebook post that its employees were "extremely distressed and worried" about her disappearance and were assisting in the search.
One of Nora's aunts, Aisling Agnew from Belfast, has set up an online fundraising campaign that aims to help cover expenses of other family members who are travelling to Malaysia to join the search effort.
