Some 180 police officers and rescuers were searching the forest on the Japan's northern Hokkaido Island, NTV reported on Monday.

They were looking for a seven-year-old boy who has been missing since Saturday afternoon, when his parents left him on the roadside.

At first, the parents said the boy disappeared while they were picking wild vegetables in the forest. However, they soon admitted they made him leave the car as form of "discipline." According to the couple, the boy was being punished for throwing rocks at people and cars while playing at a river earlier.

After driving only 500 meters (some 550 yards) away, the parents turned around to pick the boy up, according to Japanese media.

"They said they went back to the site immediately, but the boy was no longer there," a local police spokesman told the AFP news agency.

The boy's father said he avoided telling the truth because he found it embarrassing to ask for a massive search as a result of his punishment.

"I feel very sorry for my child," the father told an NTV reporter. "I am so sorry for causing trouble for many people."

Authorities warn of bears

The rescuers used sniffer dogs and horses to search through overgrown forest and tall bushes, according to NTV.

Mitsuru Wakayama, a spokesman for the nearby town of Nanae, said locals passed through the forest only occasionally.

"Not many people or cars pass by, and it gets totally dark as there are no lights," Wakayama said. "It's not surprising to encounter bears anywhere in the area."

The temperature in the forest dropped to 7 degrees Celsius (45°F) and heavy rain fell overnight, according to the media.

The police were determining whether the boy's parents should be charged with child abandonment, Kyodo News service reported.

dj/rc (AP, Reuters, AP)