KARIMABAD (Reuters) - Water began seeping out from the lake formed by a landslide in Hunza into a spillway Saturday, officials said, who added that the next one or two days are critical to avoid catastrophic flooding. If the spillway doesnt contain the water and the landslide dam bursts, authorities fear the heavy flooding could wash away many villages, bridges and roads, affecting up to 50,000 people. At this point, the water flow is very smooth but its eroding the spillway, widening it, Gilgit-Baltistans Commissioner, Asif Bilal Lohdi, told Reuters by telephone. Lets see how the water behaves in the next four to five hours, then the situation will be clear. We are on high alert, he said. Officials are hoping for a gradual erosion of the blockage, but they have not ruled out a major breach due to rising water levels from melting glaciers. The landslide in early January blocked the Hunza River and created a huge lake near Attaabad village. Twenty people were killed and another 25,000 were left stranded upstream, and now struggle to remain linked to the main town of Gilgit. The military created a spillway to drain the 19 km long and 360-feet deep lake. Lohdi said a major breach in the dam was possible. It could burst and cause flash flooding, which will ultimately wash away 34 villages and a part of the Karakorum Highway (KKH), he said referring to the main road to China. Nearly 30,0000 villagers have already been relocated to 24 camps. Head of the militarys relief organisation, Lieutenant General Nadeem Ahmed, said the erosion of the spillway and blockade would be faster in the next one or two days. These days are very crucial, he said. Before the flow of water began, the lake had already swamped at least four upstream villages, displacing nearly 6,000 people, according to aid workers and residents. The lake has also submerged a 22-km stretch of the Karakoram Highway, a trade route for a significant portion of Pakistans consumer goods from China.