BANGKOK, June 27 (Xinhua) -- The whereabouts of a missing Thai teen football team remained unknown as the rescue operations entered the fifth day amid downpours in northern Thailand's Chiang Rai on Wednesday.

The 12 children, aged between 13 and 16, together with a 25-year-old coach, have been trapped in Tham Luang cave since Saturday night as heavy rains flooded the entrance of the cave. A mother reported that her son did not return from the soccer practice that day, setting off the search.

Bicycles, shoes and backpacks of the boys were found near the entrance of the cave. Divers said footprints and handprints were discovered, reports said.

The air force brought five high-pressure electric water pumps to support the search, only to fail to handle floodwater which continues to flow into the caves, according to reports.

Rescue teams tried to drain the cave and reach the place where the football team might be taking shelter, but were blocked by the rains that caused the water level in the caves to rise.

Officials said helicopters dispatched to drop rescuers into holes by the mountain to reach the place from another side was also impossible due to rains and fog.

The Thai Navy Seal unit has been struggling through flood waters inside the cave to operate the search. Navy divers and disasters experts from other countries were also sent to help with the search.