CHICAGO (Reuters) - A jump in 3COM Corp COMS.O shares and call options on Wednesday before a $2.7 billion offer for the company was announced sparked talk that the news had been leaked, option traders and analysts said.

Hewlett-Packard Co HPQ.N announced the deal to buy the network equipment maker after the closing bell on Wednesday.

At first glance, option traders said, the hallmarks of suspicious trading were there: shares of 3Com jumped 28 cents, or 5.18 percent, to $5.69 during the day, rising from the opening bell and closing a penny off the high of the day.

After the bell, 3COM shares shot up about 35 percent at $7.65.

Option market sources said it wasn’t just the stock behaving oddly ahead of the late afternoon news. Volume in 3Com call options -- which convey the right to buy the company’s shares at a fixed price -- soared.

A total of 8,085 calls traded against only six puts. That amounted to 17 times the average daily call volume, according to option analytics firm Trade Alert.

“The rise in 3Com shares and a surge in call volume before the takeover announcement tell us that somebody’s timing was extremely good,” said Jon Najarian, co-founder of optionMonster a Web information site.

“Since I do not believe in coincidences on Wall Street, I would bet that these unusual call option trades will spark an investigation,” Najarian said.

The Securities and Exchange Commission, which looks into unusual options and share trading activity, was closed on Wednesday in observance of the Veterans Day U.S. holiday.

Options traders said the surge in 3COM call volume was focused in the November and December $5 calls, which convey the right to buy 3Com shares at $5 apiece.

“The unusual volume in the November and December $5 calls indicated a red flag and would be a sign that this news was leaked ahead of the announcement,” said Jeff Shaw, head options trader at Timber Hill, a division of Interactive Brokers Group.

Frederic Ruffy. options strategist at WhatsTrading.com, said most of the trading in the $5 call strike occurred around noon Eastern time (1700 GMT), when 3COM shares were trading at around $5.60.

Ruffy said one trade for 3,800 November $5 calls was done at a premium of 65 cents per contract. The premium for those calls closed at 65 cents, up 10 cents on the day.