PERTH, Australia (AP) — Australian police posted a 1 million Australian dollar ($750,000) reward on Thursday for information about a 4-year-old girl who officials suspect was snatched from a tent at a remote coastal location five days earlier.

Cleo Smith was reportedly last seen by her parents at 1:30 a.m. Saturday at the Blowholes Shacks campsite near the town of Carnarvon, about 900 kilometers (560 miles) north of the Western Australia state capital, Perth.

The search initially focused on the ocean on the assumption that she had wandered from the tent.

But police now say her tent’s zipper was opened by someone taller than the child.

“The positioning of that zipper for the flap is one of the circumstances that has caused us to have grave concerns for Cleo’s safety,” Western Australia Police Inspector Jon Munday said.