KUALA LUMPUR, Nov 21 (Reuters) - Malaysian crude palm oil futures jumped as much as 4.5 percent on Tuesday to reach a new 30-month high, boosting shares in listed plantation firms.

But dealers said the market, which has risen on firm soyoil prices and panic buying, was overbought and would be vulnerable to profit-taking.

"There are no fundamental factors determining the market, it is just speculative buying after soyoil went up yesterday," said one dealer. "It is heavily overbought right now and it may come down at the same pace it went up."

By the midday break, the benchmark February contract on the Bursa Malaysia Derivatives exchange was up 56 ringgit a tonne at 1,920 ringgit ($526), after rising 4.5 percent to 1,949 ringgit.

The Malaysian stock market's plantation index has surged almost 48 percent this year, fuelled by the strong crude palm oil prices and led by gains in sector bellwethers such as IOI Corp , which hit a new high of 18.8 ringgit.

Other traded months on palm oil futures were up between 38 and 56 ringgit. Overall volume surged to 14,007 lots of 25 tonnes each compared with around 4,000 to 5,000 lots traded by the end of the morning session on a normal day.

Soybean futures at the Chicago Board of Trade closed higher on Monday, lifted by the strength in corn and soybean oil amid strong speculative buying, traders said.

CBOT December soyoil ended 0.44 cent higher at 28.72 cents per lb, after reaching a contract top of 29.08. The back months closed 0.37 to 43 cent higher.

In Tuesday's electronic trading during Asian hours, CBOT soyoil was up, with the December contract trading 0.15 cent a pound higher at 28.87 cents at 0623 GMT.

Soyoil and palm oil compete for exports and their prices often move in step.

Dealers said buying in the physical market had been hit by the surge in crude palm oil prices. "Physical buying is dull, only a few deals have taken place as no one wants to pick up stocks at this level," said one trader.

Traders were offering November shipments at 1,845/1,855 ringgit a tonne. A few deals were sealed between 1,850 and 1,855 ringgit.

Exports of Malaysian palm oil products for November 1-20 fell 14.8 percent to 834,065 tonnes from the same period last month, cargo surveyor Intertek Testing Services said.

Another cargo surveyor, Societe Generale de Surveillance, said exports fell almost 9 percent to 856,664 tonnes over the same period.

Malaysia's palm oil output is expected to decline in coming months because of widespread rains during the monsoon season that started this month.

The state-run Malaysian Palm Oil Board said this month stocks at the end of October fell 11.44 percent, and output was down 13.03 percent. Exports during the month jumped 9.13 percent. ($1=3.647 ringgit)