Crude oil price further plunged 2.57 per cent to Rs 3,718 per barrel today as participants indulged in offloading their positions amid a weakening trend in Asian trade where it sank below the psychological 60- dollar mark for the first time since July 2009, analysts said. Meanwhile, West Texas Intermediate (WTI) crude for January delivery was down 86 cents at USD 59.09, while Brent crude was down 52 cents at USD 63.16 a barrel on the New York Mercantile Exchange in mid- morning trade today.