A new concrete tunnel is constructed at 240-metre level in 1957 at Ma On Shan mine slope after a heavy rainfall and landslide that covers up the original 240-metre level adit.馬鞍山礦坡240米處的礦坑入口，遭連場暴雨及山泥傾瀉掩埋後，公司於1957年為該礦坑開鑿新的三合土坑道。